JPS61108254A - Gradation recording method - Google Patents

Abstract

PURPOSE:To attain multi-grading recording without decreasing resolution by using at least >=2 kinds of contrast dots as to one color and controlling the dot number and overlap in a dot matrix. CONSTITUTION:In using a 3X3 matrix, aternary counter is used for both an X counter 17 and a Y counter 18. A light dot pattern memory 19 and a dark dot pattern memory 20 are memories using input contrast data, using X, Y addresses as address signals, and outputting respectively ON-OFF binary value light and dark dot data, and data according to predetermined dot arrangement are written. The reflected density (OD value) is different depending when a dark ink dot and a light ink dot are printed on the same location overlappingly of recording paper and they are printed on different locations, and the OD value is larger when they are printed on different locations. Multi-gradation recording, as many as 35 gradations while using a 2X2 matrix is attained by changing light/dark inks and difference between overlapped dots.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a gradation recording method, and in particular to a method for performing gradation recording using dots of at least 211 densities for one color. As an image recording method, a technique called a dither method or a density pattern method is generally used.

That is, this is a method of expressing gradation by controlling the number of dots injected into a unit matrix according to input density data. When trying to express multiple gradations using these methods, it is necessary to increase the size of the dot matrix, which results in a decrease in resolution, and the texture of the IJ pattern becomes noticeable, degrading the image quality. There were drawbacks.

For this reason, a method has been proposed in which gradation is expressed using at least two types of dots, light and dark, for the same color.

For example, Japanese Patent Application Laid-Open No. 58-59468 proposes a method of expressing gradation by using light and shade dots and changing the number of dots in a dot matrix. However, this conventional example has the disadvantage that the number of gradations that can be expressed is small because the desired gradation is expressed only by the number of dots.

<Purpose> The present invention provides gradation recording that enables multi-gradation recording even using a small dot matrix by simultaneously controlling not only the number of shading dots but also the overlap between dots. The purpose is to provide a method.

That is, the present invention actively utilizes the difference in recording density caused by changing the overlapping direction of the same number of light and dark dots to achieve multi-gradation expression.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example of the configuration of an inkjet printer embodying the present invention.

In the figure, for example, first to second multi-nozzle heads 2-1 to 2-2 are arranged in order from the left on a carriage 1, and each of the multi-nozzle heads ejects dark and light inks, respectively. Ink of each concentration is supplied from the ink tank 4 through the flexible pipes 5, respectively, and flexible insulating belts 5-1 to 5-2 each having a large number of conductive wires arranged and buried therein, relays. Drive signals are supplied via the terminal plate 6 and the integrated power supply belt 7, respectively. The carriage 1 having such a configuration is mounted on two guide rails 8, and the connected endless belt 9 is driven by a pulse motor 10 to cause the carriage 1 to reciprocate in the X direction in the figure, thereby performing main scanning. 15 and 14
A pulse motor 15 connected to a pair of rollers 14 feeds the recording paper 12 stretched out through a pair of rollers 14 in the Y direction in the figure to perform sub-scanning, and each multi-nozzle head 2-
An image is recorded using each density ink jetted from 1 to 2-2. In addition, stoppers 11-1 and 11-2 are arranged at both ends of the reciprocating path of the carriage 1 to determine the main scanning range.

FIG. 2 shows the configuration of a dot pattern generator that generates an ON-OFF binary signal to be supplied to the head of the above-mentioned inkjet printer.

The timing circuit 16 generates pulse signals called X pulse and
It is also sent to the printer and used as a timing signal during printing. In addition, the X pulse and the X pulse are simultaneously input to the input device (
(not shown) and is used as a timing signal to send the input density data to the dot pattern generator. The X counter 17 and the Y counter 1 are counters for generating an X address signal and an X address signal to select which cell in the dot matrix. Both the counter 17 and the Y counter 18 are set as quinary counters. The light dot pattern memory 19 and the dark dot pattern memory 20 use the input density data and the
This is a memory that outputs dark dot data, and the data is written in accordance with a predetermined dot array configuration. The printer 21 is a printer as shown in FIG. 1, and uses the supplied light dot data, dark dot data, 10 controls etc. are performed.

When dark ink dots and light ink dots are overprinted at the same position on recording paper, and when they are overprinted at different positions, the reflection density (OD value) does not last the same, and the OD value is higher when they are placed side by side. Comes off. The reason for this is that when overprinting, the amount of ink that is ejected at the same position increases and the dot area expands, but the amount of dot spread is small, and especially in inkjet printers, recording paper with good absorbency is generally used. Because of this, the dots do not spread out very much even if the amount of ink increases, and even in areas where dark and light inks overlap, the dye penetrates into the depth of the paper, so the OD value of each dot is different from the OD value of each dot. It is conceivable that it will be smaller than the sum of . Therefore, by utilizing the effect of , multiple gradations can be expressed even using a small dot matrix, and high-quality prints with high resolution and gradation can be obtained.

The number of gradation levels that can be expressed using this recording method is given by the following equation.

However, T: number of gradation levels expressed by the dot matrix m-n; dot matrix size l: number of multilevels (if shading 2 @! = 6.5 types! = 4
). The table below shows the number of gradations that can be expressed using this formula when changing the matrix size and the number of multi-value levels.

Figure 6 shows the matrix size 2 x 2. An example of how to place dots when J=5 is shown. In the case of binary recording using one type of ink, only 5 gradations could be expressed, but by adding shading and changing the difference in the overlap of dots, 555 gradations can be expressed in a 2 x 2 matrix. It enables gradation recording. The number of recordable gradations can be dramatically increased by increasing the dot matrix size and the number of multi-values.

When actually writing data to the dot pattern memory 19, 20, for example, print grayscale patches with a dot pattern as shown in Figure 5, measure the OD value of each patch, and measure the OD value. Sort them in ascending order, and adjust them so that they match human visual sensitivity, that is, so that the OD value of the print has a linear relationship with the input density data.
All you have to do is make a correspondence between the input density data and the dot pattern, and then write the data into the dot pattern memory.

Although the above embodiments have been described using monochromatic dots, this can of course be extended to color, and can be realized by using dots for each of Y, M, and O.

Furthermore, although this embodiment has been described using an inkjet printer as an example, it is of course applicable to any type of printer that forms images on dots, such as a thermal transfer printer.

Effect> As explained above, by using at least two or more types of shading dots for each color and controlling the number of dots and their overlap in the dot matrix, it is possible to obtain dots without reducing resolution.
Multi-tone recording became possible.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of an inkjet printer, FIG. 2 is a block diagram of a dot pattern generator that generates a dot pattern according to the present invention, and FIG. 5 shows an example of a dot matrix formed according to the embodiment. FIG. 1... Carriage 2-1 to 2-2... Inkjet head 5... Flexible pipe 4... Ink tank 5-1 to 5-2... Flexible insulating belt 6... Relay terminal plate 7...Comprehensive power supply belt 8...Guide rail 9...Endless belt 10.15...Pulse motors 11-1 to 11-2...Stopper 12...Recording paper 15.14 ... Row 2 vs. 16 ... Timing circuit 17-18 ... Counter 19-20 ... Dot pattern memory 21 ... Printer

Claims (1)

[Claims] In a gradation recording method that performs gradation recording by controlling the number of dots formed in a dot matrix according to input density information using at least two types of dot forming means, shading and light, for the same color, the number of shading and light dots is A gradation recording method characterized by performing gradation recording by a combination of and overlapping.