CN1310760C - Printing data generation method suitable for printing with different ink droplet sizes - Google Patents

Abstract

The invention is a printing data generating method suitable for printing with different ink droplet sizes, it is suitable for the printing apparatus which outputs the ink droplet of different size with the multiple ink gun, mainly find all combination modes according to the number of ink gun, and the number of ink droplet that each ink gun can output first, the color saturation that various combination modes present builds up and forms the half tone valve table (halftone threshold); when the image data to be printed is input, each pixel of the image data corresponds to one of the proper combination modes, namely a halftone coding value, according to the halftone threshold table, wherein the coding value can be decomposed into a plurality of groups of bits (bits), each group directly corresponds to the number of ink drops charged by a single ink jet head, and the printing data processing process can be simplified and the printing efficiency can be improved by the mode of directly driving each ink jet head to print.

Description

Printing data generation method suitable for printing with different ink droplet sizes

technical field

The invention relates to a printer, in particular to a printing data generation method suitable for printing with different ink droplet sizes.

Background technique

Drop-on-Demand Ink Jet Printing (Drop-on-Demand Ink Jet Printing) is to use the inkjet head to reciprocate on the paper, and drive the nozzle hole of the inkjet head to the position where the ink drop is to be sprayed to complete the printing work. In order to present the photographic quality of today's inkjet printing, the printing result must have rich color gradation changes; that is, a certain printing color (such as C, M, Y), at any pixel position on the paper ( Pixel location), must be able to produce different levels of changes from light to dark (for example, 8 changes from no spray, light to deepest), so that through the combination of C, M, Y these primary colors (Primary color), It can construct rich colors and color gradation changes, and meet the requirements of photo quality.

This level change from shallow to deep can be achieved by multi-drop printing, that is, multiple ink drops are sprayed on the same position to achieve multi-level printing in color. Effect. However, since multi-ink droplet printing needs to be achieved through the technique of multi-pass printing, the inkjet head must perform repeated reciprocating movements to accumulate and spray the required drops on all pixel positions in sequence. number. As a result, its overall printing speed (Throughput) is limited, resulting in the result that photo-quality printing usually takes a long time.

In order to achieve the so-called photo image quality and make the printed results have a more continuous tone, the most important key is to maximize the amount of color at each pixel position, and its necessary condition is the inkjet Ink droplets must be smaller. The early inkjet ink drop size is relatively large, about 80 to 100 pl. The color changes that can be produced are relatively small. The photo resolution enhancement technology (PhotoREt, photo resolution enhancement technology) proposed by Hewlett Packard (Hewlett Packard) provides a solution. With the development of production technology, the currently launched For a color inkjet head (three-color, CMY), the output ink drop is only about 10pl, and at any pixel position, one color can spray up to 8 ink drops. For this kind of inkjet head, if 0, 1, 3 or 8 ink drops of a single color are used at a pixel position, 4 different color levels from white to darker can be obtained. If combined with the result of color mixing, it can directly produce more than 250 kinds of printable colors, greatly increasing the number of color levels and the richness of colors.

As for the printing principle of an inkjet printer, the printing principle is as follows: when an image is to be printed, the input image data (Image data) is first processed by a halftoning process, that is, the input image data is converted into inkjet ink drop dots. information. For example, when the early ink droplet size is large, there is only a choice of spraying a single drop of ink or not spraying ink at a single pixel position. Therefore, if the input image data has a color scale that is represented by 8 bits as a continuous sequence from 0 to 255 value, the halftone processing method is to take the middle value of the color scale (ie 127) as the halftone threshold (Halftoningthreshold), the pixels exceeding this value are sprayed with a drop of ink, and the pixels less than or equal to this value are not dotted . After this half-tone process, the original 8-bit pixel can be represented by 1 bit (0/1, not sprayed/sprayed), which is the most basic half-tone processing method.

With the development of photo-quality printing technology mentioned above, zero to several ink droplets need to be sprayed on each pixel position to increase the variation of color gradation. For this kind of multi-drop printing, each pixel position not only needs to provide the information of spraying or non-spraying, but also needs to consider the depth information of the color. If the multi-ink droplet printing method with the same droplet size is used, the color depth is achieved by the number of ink droplets. Obviously, when printing has to consider more conditions (printing or not, color depth), the above-mentioned halftone processing method represented by 1 bit cannot be satisfied.

If 2 bits are used to represent four levels from 0 to 3, these four levels can be used to indicate the depth of the color that should be sprayed on the pixel position. The halftone method corresponding to this can divide the above-mentioned 0-255 continuous color scale into four segments equally, that is, the halftone critical value is 63, 127, 191. The input image data of {0, 63}, {64, 127}, {128, 191}, {192, 255} respectively will correspond to the four level values of 0-3, that is, expressed in 2bits 00, 01, 10, 11. This kind of halftone processing that exceeds 1bit is also called multi-bit or multi-level halftone (Multi-level or Multi-bit halftoning process) program.

After halftone processing, after obtaining the level corresponding to each pixel position, it is further determined how many ink droplets should be used to express the requirements of each level. Taking the above-mentioned 4 level values as an example, the number of ink drops required to meet each level value can be found out by the following steps: First, determine the highest allowable number of drops of ink of each color on a single pixel. The number of drops may be that the color depth (density) can no longer be further distinguished, or it has exceeded the allowable range of the paper, and the ink drop range (dot area) begins to exceed the pixel position. Taking the aforementioned color inkjet head as an example, it is 8 Drops are the upper limit. Next, the possible number of drops for printing (here 0 to 8 drops) was sprayed onto the paper, and the color density thereof was measured respectively. Since the target is divided into 4 color levels (level), the number of drops corresponding to 0%, 33%, 66%, and 100% of the saturation can be obtained as a result of {0, 1, 3, 8} drops, such as As shown in Figure 4, the vertical axis (y-axis) represents the color saturation, while the horizontal axis (x-axis) represents the number of ink drops, and these corresponding drop values will be used to achieve the requirements of each level of color gradation during printing. In other words, the above-mentioned input image data respectively located at {0, 63}, {64, 127}, {128, 191}, {192, 255} will be respectively represented by {0, 1, 3, 8 } drops to achieve.

The aforementioned technology is illustrated by taking the ink droplet size provided by the inkjet head as an example. If the printer can provide ink droplets of different sizes, the printing work can be completed with a small total number of drops by an appropriate combination of large and small ink droplets. . For example, in the case of U.S. Approved Patent No. 5,917,510, the Drop-on-Demand inkjet head based on the piezoelectric (Piezo) principle is used to control the inkjet head to eject Corresponding to ink droplets of different sizes, in order to achieve the purpose of printing ink dots of different levels, the halftone processing method of this patent is the general error diffusion method (Error diffusion). This patent requires an inkjet with the ability to control the ink droplet size head, its cost and control requirements are relatively high, and there are also restrictions on the selection of inkjet heads. Furthermore, when the level value obtained by the halftone processing wants to control the inkjet head to output an appropriate amount of ink droplets, it must go through an analysis step to interpret the level value to determine which inkjet heads must output, and then interpret the necessary output. How many ink droplets are output, this two-stage analysis method makes it impossible to increase the data processing speed.

Contents of the invention

In view of the disadvantage that the speed of the multi-ink droplet printing method in the prior art cannot be increased, the main purpose of the present invention is to provide a printing data generation method for printing with different ink droplet sizes, which is suitable for multiple inkjet heads to output different The ink drop size printing device can convert and encode the color scale value of the image data into an appropriate data format, and use the encoded data to individually control each inkjet head, thereby improving printing efficiency.

The printing data generation method suitable for printing with different ink droplet sizes provided by the present invention comprises the following steps:

Establish a half-tone threshold value table, and calculate the color saturation that can be presented by each combination method based on P types of ink droplet sizes and all combinations that can provide N types of ink droplet numbers, and establish according to the relationship between the combination method and the corresponding saturation Half-tone threshold value table; wherein, the aforementioned P and N are positive integers not equal to zero;

A multi-level half-tone coding data is generated by using the aforementioned threshold value table, which is used to drive the inkjet head to output the number of ink droplets corresponding to the size of the ink droplet, so as to print out the image data.

There are (N+1) ^P types of the above-mentioned combinations.

According to the above method of the present invention, the output halftone coded data is obtained by combining P types of ink droplet sizes and N types of ink droplet numbers.

According to the above method of the present invention, the P types of ink droplet sizes are output by P inkjet heads.

According to the above method of the present invention, the P types of ink droplet sizes are output by a single inkjet head.

According to the above method of the present invention, the halftone coded data can be disassembled into P groups, and each group uses X bits of data to represent the number of N types of ink droplets, where 2 ^X =N.

According to the above method of the present invention, the halftone coded data can be disassembled into P groups, and each group is correspondingly output to each inkjet head, wherein each group uses X bits of data to represent the data of the inkjet head. The number of ink droplets to be ejected, where 2 ^X =N.

With this method, the input image data can be efficiently printed with ink droplets of different volumes through the halftone processing procedure, achieving high-quality presentation of color gradation, and greatly increasing the printing speed.

Description of drawings

Fig. 1 is a graph of ink drop combination and color saturation in the present invention.

Fig. 2 is another graph of ink drop combination and color saturation in the present invention.

FIG. 3 is an action block diagram of the method for generating data prints according to the present invention.

FIG. 4 is a graph of ink drop combination and color saturation in the prior art.

Detailed ways

The invention proposes a method for generating printing data, which is mainly applicable to printing devices that can produce different ink droplet sizes for printing. The printing device can output ink droplets of several different sizes through a single inkjet head, or multiple It is composed of inkjet heads corresponding to different ink droplet sizes, but in the following detailed description, the present invention takes a composite printing device with multiple inkjet heads as an example. When an image data to be printed is to be output to the printer, because each pixel of the image data is originally represented by a continuous color scale value, it must be converted into a data format that can be interpreted by the printer to drive the inkjet head for printing. The present invention It includes two main technical means, one is the establishment of the halftone threshold table (Halftoningthreshold table), and the other is to convert the color scale value into halftone coded data according to the threshold table, and then directly output to each inkjet head. The following is a detailed description:

(1) Establishment of halftone threshold table

A composite inkjet printer is an inkjet printer with a plurality of inkjet heads, assuming that the printer has P numbers of inkjet heads that can provide the same color and different ink droplet sizes (so it can also be regarded as having P kinds of ink droplet sizes ), and the printing stroke is at most N times, that is, Npass printing (each inkjet head can only print N drops in the same pixel position at most), then the most possible inkjet combinations on a single pixel are (N+1 ) There are as many types of ^P , and the aforementioned P and N parameters are all positive integers greater than zero. For example, if the printer has P=2 inkjet heads, which respectively provide ink droplets of two different ink droplet sizes but the same color, and print with N=2pass at most, then the possible printing combinations on a single pixel position are ( 2+1) ² = 9 kinds, the combination of which is:

Drop#of P1/P2 = {0/0, 0/1, 0/2, 1/0, 1/1, 1/2, 2/0, 2/1, 2/2}.

Assuming that the printable ink droplet sizes of the two inkjet heads P1 and P2 are 10pl. (pico-liter) and 30pl. respectively, the above nine combinations can be formed as follows. The number of ink drops of the first inkjet head P1 (10pl.) The number of ink drops of the first inkjet head P2 (30pl.) Total number of ink drops (pl.) Saturation (density,%) Color scale value (0~255) 0 0 0 0 0 0 1 30 37.5 96 0 2 60 75 192 1 0 10 12.5 32 1 1 40 50 128 1 2 70 87.5 224 2 0 20 25 64 2 1 50 62.5 160 2 2 80 100 255

It can be seen from the above table that there are nine combinations of saturations of different degrees mentioned above, and only two printing strokes (2pass) can be combined to form nine different total ink droplets. When these combinations of ink droplets are sprayed onto the paper, the color saturation (density) of the ink dots produced will also be different. By measuring the saturation, the relationship between saturation and these nine combinations can be found curve.

As shown in Figure 1, it means that under (N+1) ^P combinations (shown on the X-axis), the relationship curves of different color saturations (shown on the Y-axis) can be presented, and the inkjet head with the highest saturation The combination with the number of drops is the deepest color that this hybrid inkjet printer can express, while the combination without any ink dots represents the minimum saturation. If the highest saturation is set as 100%, and the minimum is set as 0%, taking the input image data of 8bit (color scale value 0-255) as an example, the color scale value 255 corresponds to 100% density, and the color scale A value of 0 corresponds to 0%. According to the saturation (density) value corresponding to each combination in Figure 1, according to the ratio (the position of these ratios is marked on the Y axis) corresponding to the interval from 0 to 255, the critical value of each halftone level can be obtained value. The combination of the results obtained through this process is used as the content of the halftone threshold table (Halftoning threshold table), which is used as the basis for halftone conversion.

It can be seen from Figure 1 that among the many combinations of inkjet heads and the number of drops, there may be several combinations that produce ink dot saturations that are very similar or identical during printing, such as combination 5 and combination 6 in the figure. In other words, the hybrid inkjet head printer can utilize several different combinations of ink droplet sizes and drop counts to produce similar saturation levels. Therefore, when establishing the halftone threshold table (Halftoningthreshold table), if the saturation difference caused by some of the combinations is smaller than a certain preset value, it is not necessary to regard these similar saturations as different levels. Take a representative value.

(2) Halftone coding

According to the aforementioned halftone threshold table, the continuous color scale of the input image data can be classified into multi-level halftones, and the hierarchical values obtained after classification can be represented by a series of bit data. The result after tinting, that is, the encoding result.

For composite inkjet head printers, the printing action is completed by inkjet heads with different ink drop sizes in combination with multi-pass and multi-drop printing. Therefore, after halftone The encoded digital data is output to the drive module of each inkjet head to complete the inkjet action. The multi-level halftone processing in the prior art is to represent the number of separable levels with several bits. In other words, it is an encoding process. For example, if through the halftone valve The value table can be divided into 8 levels, and the halftone result can be represented by 3 bits to distinguish each level from level 0 to level 7, which are 000, 001, 010, 011, 100, 101, 110, 111 .

According to the foregoing, in the half-tone method proposed by the present invention, a series of digital output data is printed by a plurality of inkjet heads with different ink droplet sizes, and the digital data is used to indicate each inkjet head. If the number of ink drops required to be sprayed by the ink head is used as the code of the digital data directly by the total number of layers that can be generated, the printer needs to go through a process of identification and analysis after receiving the string of digital data. Correspondingly, the printing on each pixel position is achieved by those inkjet heads and how many ink droplets must be sprayed, which will lead to a decrease in printing efficiency.

In order to avoid the reduction in efficiency caused by the drive module having to further find the appropriate inkjet head and ink droplet number when the halftone output data is output to the subsequent drive module, the present invention proposes a coding method, The inkjet head can be directly driven to output the required number of ink droplets to improve data processing efficiency and simplify the control system. The following is a detailed description.

First of all, it must be emphasized that this encoding method does not sequentially perform digital encoding according to the saturation level value (density level) of halftone processing. Not represented by the corresponding 000-111.

On the contrary, the encoding method of the present invention will simultaneously include the information of the inkjet head and the number of printing ink droplets. Firstly, for each inkjet head, the number of ink droplets it can provide is used for sequential coding. Of course, the maximum number of ink droplets that can be provided cannot exceed the number N of printing passes.

As far as each inkjet head is concerned, it must be represented by the number of bits sufficient to indicate that the inkjet head provides all possible ink droplet number combinations. For example, if N=3, and the inkjet head can print in 3pass Provide 0, 1, 2, 3 drops of ink to a pixel position, and to encode the number of ink drops of the inkjet head, at least 2 bits of data must be used to represent the 4 combinations of drop numbers.

Then, combine the multi-bit encoding results of all the inkjet heads into a final halftone output value, and send this value to the printer as the printed data.

Therefore, if there are 2 inkjet heads printing a 3pass composite inkjet printer (P=2, N=3), and each inkjet head provides the number of ink drops of 0, 1, 2, and 3 drops, then the total must be Take the 4 bits of a ₁ a ₂ a ₃ a ₄ as the output of the halftone result of this system, where a ₁ a ₂ represents the number of ink drops that the first inkjet head must output, and a ₃ a ₄ represents the second inkjet head The number of ink drops that the inkhead must output.

Please refer to FIG. 2 , the following is a detailed explanation of the present invention using a complete embodiment.

Assuming a composite inkjet head printer has 2 inkjet heads, printing 3pass, each inkjet head can eject 0, 1, 2, 3 drops of ink in this 3pass, a total of (3+1) ² can be combined = 16 ink drop concentrations. Since each inkjet head has 4 ink droplet levels (level 0-level 3), each level is coded with 2 bits. Therefore, all possible combinations of printing ink dots provided by the two inkjet heads have a representation of 2bit+2bit=4bit.

In Fig. 2, the code numbers on the X-axis are formed by combining the codes of the two inkjet heads. For example, binary data: 0110(6), that is, the number of ink drops (1 drop) that the first inkjet head ejects level 1 (binary: 01); while the second inkjet head ejects level 2 ( binary: 10) the number of ink drops (2 drops).

After all the 16 printing combinations are printed, the ink dot saturation produced by each combination is measured, and the curve shown in Figure 2 can be obtained. It can be seen from the figure that in the range of density 0% to 100%, a total of 12 intervals can be distinguished, and the data points on the graph are used as the nodes of the intervals.

These nodes representing different color saturation levels will be allocated according to the ratio, and the input image data (continuous color scale value) will be halftone in the interval (for example, 0 to 255).

After the halftone processing is completed, the encoded output data is still encoded according to the original X-axis in Figure 2, rather than sequentially encoded from low density to high density.

Please refer to FIG. 3 , through the above method, when an input image data is processed by the halftone threshold table (Halftoning threshold table) of the present invention, it is outputted through the encoding of the inkjet head and the number of ink droplets. The output coding data can be disassembled into arrays according to the number of inkjet heads, and sent to the corresponding inkjet head printing data processing modules, and then sent to the inkjet driving modules of each inkjet head to complete the printing data Actions.

To sum up, the method proposed by the present invention is to encode each inkjet head and its ink droplet number first, and then form a halftoning threshold table (Halftoning threshold) from each data point after obtaining the printed saturation (density). table), and in the process of halftone encoding, the input pixel data points classified into a certain interval, that is, the corresponding encoding values are used as the output data. In this way, the output data can be directly decomposed into several groups of bits, and each group directly corresponds to an inkjet head (the original code is a combination of individual codes of each inkjet head). Therefore, the multi-bit output of halftone can be directly sent to the drive module of each inkjet head, so that each inkjet head can print through multi-pass and mutli-drop according to the halftone value it receives. In this way, the corresponding number of ink droplets is sprayed, so that the process of printing data processing can be simplified, and each inkjet head can be driven efficiently.

Claims (7)

1. A method for generating printing data suitable for printing with different ink droplet sizes, comprising the following steps: Establish a half-tone threshold value table, and calculate the color saturation that can be presented by each combination method based on P types of ink droplet sizes and all combinations that can provide N types of ink droplet numbers, and establish according to the relationship between the combination method and the corresponding saturation Half-tone threshold value table; wherein, the aforementioned P and N are positive integers not equal to zero; A multi-level half-tone coding data is generated by using the aforementioned threshold value table, which is used to drive the inkjet head to output the number of ink droplets corresponding to the size of the ink droplet, so as to print out the image data. 2. The printing data generation method suitable for printing with different ink droplet sizes as claimed in claim 1, characterized in that: there are (N+1) ^P types of combinations. 3. The printing data generation method suitable for printing with different ink drop sizes as claimed in claim 1, characterized in that: the outputted halftone coded data is obtained by combining P types of ink drop sizes and N types of ink drop numbers obtained by encoding. 4. The printing data generating method suitable for printing with different ink droplet sizes as claimed in claim 1, wherein the P types of ink droplet sizes are output by P inkjet heads. 5. The printing data generation method suitable for printing with different ink droplet sizes as claimed in claim 1, wherein said P types of ink droplet sizes are output by a single inkjet head. 6. The printing data generation method suitable for printing with different ink droplet sizes according to claim 1, characterized in that: the halftone coded data can be disassembled into P groups, and each group is represented by X The one-bit data represents the number of N types of ink droplets, where 2 ^X =N. 7. The printing data generation method suitable for printing with different ink droplet sizes according to claim 4, characterized in that: the halftone coded data can be disassembled into P groups, and each group is correspondingly output to For each inkjet head, each group uses X bits of data to indicate the number of ink droplets that the inkjet head needs to eject, where 2 ^X =N.

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