JP2000062154A - Image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the drying time of a print sheet while preventing strike- through by controlling the quantity of ink drop depending on the density of an image to be printed. SOLUTION: A pixel data of predetermined size around a pixel to be printed is fetched from a line memory (Step S301) and mean density level thereof is calculated (Step S302). A decision is then made whether the mean density level is higher than a predetermined level or not (Step S303) and if it is higher than the predetermined level, a current pixel data having lowered density level is outputted, as a pixel data of the pixel to be printed, to a head controller (Step S304). If it is lower than the predetermined level, the current pixel data is outputted, as it is, to the head controller (Step S305).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method, and more specifically, to controlling ejection of ink droplets onto recording paper in an image recording apparatus using an inkjet head capable of multi-gradation expression. An image recording method.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for recording a high-quality (high-quality) image, there is a recording apparatus using an ink jet head capable of expressing multiple gradations. Here, the ink jet head is a head device having a plurality of ejection ports for ejecting ink droplets, and ejects the ink droplets from the corresponding ejection ports on the basis of the image to be recorded and attaches them to the recording paper, Is formed. And
Multi-tone expression is possible by controlling the size of the ink droplets ejected by the inkjet head.

[0003]

In the recording apparatus using this ink jet head, since the ink droplets are ejected and adhered to the recording paper as described above, the spread of the ink on the paper when the ink adheres is caused by the mechanism. Then, a part where the separately ejected inks overlap is generated. For this reason, especially in solid printing (printing in black) or printing requiring a large amount of ink such as high-density printing, it takes a long time to dry the printing paper in the area where the ink overlaps. In addition, there is a problem that the show-through of the recording paper (a phenomenon in which the ink attached to the front surface oozes out to the back surface) occurs.

Therefore, an object of the present invention is to provide an image recording method for controlling the amount of ink droplets corresponding to the density of an image to be printed, thereby shortening the drying time of printing paper and preventing show-through. That is.

[0005]

The first aspect of the present invention is an image recording method in an image recording apparatus using an ink jet head capable of multi-gradation expression. At least a line memory for storing pixel data having an instructed density level (higher levels instruct darker recording) and head control means for controlling ejection of ink droplets of the inkjet head according to the density level are provided. , A step of retrieving pixel data of a predetermined size centering on a pixel to be printed (hereinafter referred to as a pixel to be printed) from the line memory, and an average of respective density levels of the retrieved pixel data of the predetermined size The step of calculating the value (hereinafter referred to as the average density level) and the calculated average density level are set to a predetermined level. Determining whether a le above, when the average density level is a predetermined level or more in the determining step, and a step of changing the density level of the printed pixel to a lower level,
When the density level is changed in the changing step, the head control means controls the ejection of the ink droplets of the inkjet head according to the changed density level.

As described above, according to the first aspect of the present invention, the average density level of the pixel to be printed and the pixels around it is determined, and only when the average density level is equal to or higher than a predetermined level, the object to be printed is Decrease the pixel density level. As a result, the ink amount can be reduced only for the solid print portion and the high-density print portion close thereto. Therefore, according to the first aspect of the invention, it is possible to reduce the total consumption of the ink amount without affecting the deterioration of the image quality, shorten the drying time of the recording paper, and prevent the show-through and the deflection. Furthermore, the power consumption of the heater for drying the recording paper can be reduced.

In a second aspect based on the first aspect, the predetermined size is M × M (M
Is a square with an odd number of 3 or more.

As described above, according to the second invention, the first
In the invention, the predetermined size is an M × M square in which one side is an odd number M of 3 or more. Therefore, according to the second aspect, the pixel data in which the pixel to be printed is located at the center of the size can always be taken out, and more accurate calculation of the average density level and the level determination can be performed.

[0009]

1 is a block diagram showing a part of the configuration of an image recording apparatus using an image recording method according to an embodiment of the present invention. 1, the image recording apparatus using the image recording method according to the embodiment of the present invention includes a line memory 10, a data analysis unit 20, a head controller 30, and a recording head 40.

The line memory 10 stores image data supplied from another component (not shown) of the image recording apparatus in a buffer for each line (first line to Nth line). The data analysis unit 20 takes out a plurality of necessary pixel data (image data of one pixel) from the line memory 10, analyzes the data, and outputs pixel data based on the analysis result to the head controller 30. The value of N is determined by the size of the pixel data to be extracted. The head controller 30 controls the recording head 40 according to the pixel data received from the data analysis unit 20. The recording head 40 is an inkjet head capable of multi-gradation expression, and ejects corresponding ink droplets under the control of the head controller 30.

The data analysis performed by the data analysis unit 20 will be specifically described below with reference to FIGS. 2 and 3. Figure 2
FIG. 4 is a diagram showing an example of the size of pixel data extracted from the line memory 10 by the data analysis unit 20. FIG. 3 is a flowchart showing a data analysis process performed by the data analysis unit 20. As a precondition, in the following description, the density of each pixel is given in 8 gradations “level 0” to “level 7” of 3-bit data, and “level 0” indicates a white spot with the lowest density. It is assumed that "level 7" represents a solid black state having the highest density.

First, as shown in FIG. 2, the data analysis unit 20 analyzes the data of an arbitrary pixel. As shown in FIG. 2, the pixel of the data analysis, that is, the pixel to be printed (the hatched portion in FIG. 2). Hereinafter, 5 × 5 size pixel data centering on the print target pixel) is extracted from the line memory 10 (step S301). In this example,
The number of buffers required in the line memory 10 is the first
There are five lines, line 5 to line 5. The data analysis unit 20 then averages the respective density levels of the extracted 5 × 5 size pixel data (hereinafter referred to as the average density level).
Is calculated (step S302). The average concentration level is
For example, it may be calculated by adding all the density levels of the pixel data of 5 × 5 size and then dividing by the total number of pixels “25”.

If the pixel to be printed is a page edge pixel, pixel data of 5 × 5 size cannot be extracted, so only the pixels that can be extracted (for example, in the case of a corner pixel, 3 pixels). After calculating the average density level with x3 size pixel data or complementing the pixel data of the pixel part that cannot be extracted (for example, the density level 6 is complemented as the pixel data of the pixel part that cannot be extracted). ) The average density level may be calculated.

Next, the data analysis section 20 determines whether or not the average density level calculated in step S302 is "level 6" or higher (step S303). In the determination of step S303, if the average density level is equal to or higher than “level 6”, the data analysis unit 20 changes the current density level by one level (for example,
If "Level 7", change to "Level 6", "Level 4"
If so, the pixel data is changed to "level 3", and the changed pixel data is output to the head controller 30 as pixel data of the pixel to be printed (step S304). On the other hand, if it is determined in step S303 that the average density level is not equal to or higher than "level 6", the data analysis unit 20 does not reduce the density level and uses the current pixel data as the pixel data of the print target pixel as the head controller 30. (Step S305).

When the data analysis unit 20 completes the data analysis process (that is, the determination of the density level) of the steps S301 to S305 for any one pixel, all the data analysis processes of the steps S301 to S305 are performed. It is determined whether or not it has been performed for the pixel, and if there is a pixel for which data analysis processing has not been performed yet, the process returns to step S301 and shifts to data analysis processing for the next pixel (step S306). By repeating the above steps, the data analysis unit 20 outputs the density levels of all the pixels to the head controller 30.

In the image recording method of the present invention, since the density level changed (lowered) in step S304 is not fed back to the line memory 10 as described above, the above-mentioned steps suitable for all pixels are used. The determination in S303 can be performed.

The head controller 30 controls the recording head 40 according to the density level of each pixel data continuously sent from the data analysis unit 20, that is, the ink ejected from the ink jet head at the corresponding pixel position. Control the size of each drop.

As described above, in the image recording method according to the embodiment of the present invention, the average density level of the pixel to be printed and the surrounding pixels is judged, and the average density level is equal to or more than the predetermined value. Only, the density level of the pixel to be printed is lowered. As a result, the ink amount can be reduced only in the central portion of the solid print portion or the high density print portion close thereto. Therefore, according to the image recording method according to the embodiment of the present invention, it is possible to reduce the total consumption of the ink amount without affecting the deterioration of the image quality, and shorten the drying time of the recording paper. It is possible to prevent show-through, bending, etc., and further reduce the power consumption of the heater for drying the recording paper.

In the above embodiment, the case where the pixel data of 5 × 5 size centering on the pixel to be printed is taken out from the line memory 10 is described as an example when the data analysis of an arbitrary pixel is performed. However, the image recording method of the present invention can of course be realized with a size other than this 5 × 5 size.

Further, in the above-described one embodiment, it is described that the data analysis unit 20 determines in step S303 whether or not the average density level calculated in step S302 is "level 6" or higher. However, the level determined by the data analysis unit 20 is not limited to the described “level 6”, and can be freely determined according to the purpose or use of printing. Needless to say, the density of each pixel is the same as the above-mentioned 8-gradation “level 0” of 3-bit data.
The same can be applied to cases where the level is other than "level 7".

Further, in the above-described embodiment, the data analysis unit 20 performs the step S304 in the step S304.
As a result of the judgment in 303, the average density level is “level 6”.
If it is above, as the pixel data of the print target pixel,
It is described that pixel data obtained by reducing the current density level by one level is output to the head controller 30. However, the density level lowered by the data analysis unit 20 at the time of this determination is not limited to the one level described above, and can be freely determined according to the purpose or use of printing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a part of a configuration of a printing apparatus using an image recording method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a size of pixel data extracted from the line memory 10 by the data analysis unit 20.

FIG. 3 is a flowchart showing a data analysis process performed by a data analysis unit 20.

[Explanation of symbols]

10 ... Line memory 20 ... Data analysis unit 30 ... Head controller 40 ... Recording head

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA04 EA05 EA06 EB41 EB58                       EC07 EC42 EC70 EC75 EC79                       ED01                 2C057 AF25 AF27 AF39 AL31 AM28                       CA01

Claims (2)

[Claims] 1. An image recording method in an image recording device using an inkjet head capable of multi-gradation expression, wherein the image recording device indicates a density level indicating a recording density (a higher level indicates a darker recording. A line memory for storing pixel data having a print target pixel (hereinafter, referred to as a print target pixel), and a head control unit for controlling ejection of ink droplets of the inkjet head according to the density level. A step of extracting pixel data of a predetermined size centered on a target pixel) from the line memory; and an average value of the density levels of each of the extracted pixel data of the predetermined size (hereinafter referred to as an average density level). ) Is calculated, and the calculated average density level is equal to or higher than a predetermined level. A step of determining whether or not, when the average density level in the determining step is equal to or higher than the predetermined level, changing the density level of the print target pixel to a lower level, If the density level is changed in the changing step, the head control means controls ejection of ink droplets of the inkjet head according to the changed density level. . 2. The image recording according to claim 1, wherein the predetermined size is an M × M (M is an odd number of 3 or more) square centered on the pixel to be printed. Method.