JP3033687B2 - Multicolor printing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-color printing apparatus, and more particularly to a multi-color printing apparatus for performing multi-tone printing.

[0002]

2. Description of the Related Art Conventionally, a multi-color printing apparatus of this type generally prints three or four colors to form a multi-color print. Color shift occurs. In particular, color misregistration appears remarkably at the color boundary, and the ground color of the printing paper is seen through or black streaks occur.

As a method for preventing color misregistration, Japanese Unexamined Patent Publication No.
Japanese Patent Application Publication No. 134134/1994 proposes a method shown in FIGS. A CCD line sensor 14 is provided between the thermal head 11 and the photo sensor 13, respectively. The mark provided on the recording paper 12 is detected by the CCD line sensor 14. Here, the recording paper 12 is positioned at the reference position 1
5, the thermal head 11 is always moved by the CCD line sensor 14 detecting the shift amount d and correcting the position of the recording unit including the thermal head 11 by that amount. A fixed positional relationship with respect to the recording paper 12 can be maintained.

Japanese Patent Application Laid-Open No. 64-49062 proposes a method shown in FIG. The mark given to the printing paper is detected by the mark detecting means 22y, 22m, 22c. The control means includes the respective printing means 21y, 21
The printing timing of each color is controlled by controlling the timing of giving printing data in m and 21c. If the printing paper is shifted back and forth for some reason after the printing by the printing means of a certain color is completed, the transport time of the printing paper from the printing means to the printing means of the next color is also Back and forth compared to when there is no gap. This time lag is detected by the mark detecting means 22y, 22m, 22c, and the control means corrects the printing timing according to the time lag. This reduces color shift.

[0005]

In the above-described conventional multicolor printing apparatus, if the overlay is shifted due to a printing mechanism or a poor precision of the paper conveyance, a color shift occurs in an obtained image.
In particular, there is a problem that color misregistration appears remarkably at a color boundary portion, and the ground color of the printing paper is seen through or black streaks are generated. In the method proposed in Japanese Patent Application Laid-Open No. 61-134274, a mark is put on a part of the printing paper, so that the printing unnecessary for the user is performed. Since it is necessary for the paper traveling section, there is a problem that the apparatus becomes complicated and expensive. On the other hand, the method proposed in Japanese Patent Application Laid-Open No. 64-49062 has the same problem. In addition, there is a problem that alignment can be performed only in the paper traveling direction, in other words, in the sub-scanning direction.

An object of the present invention is to make color misregistration inconspicuous at a color boundary where color misregistration is noticeable without performing unnecessary printing for a user, making the apparatus complicated and expensive. SUMMARY OF THE INVENTION It is an object of the present invention to provide a multicolor printing apparatus in which the ground color of printing paper is not transparent.

[0007]

SUMMARY OF THE INVENTION A multicolor printing apparatus according to the present invention has a processor for calculating the contents of a print data memory, and each of at least two of a plurality of colors to be superimposed.
When the print data of adjacent dots has a difference equal to or greater than a certain value, the processor performs an operation of adding and subtracting the mutual data based on a certain rule.

The multicolor printing apparatus according to the present invention subtracts high-value data, adds low-value data among print data of adjacent dots, and ensures that high-value data is higher than low-value data even after correction. It may be.

In the multicolor printing apparatus according to the present invention, the calculation method may be changed depending on the color tone of the dot.

In the multicolor printing apparatus according to the present invention, the print data of adjacent dots and the print data of dots located in the vicinity thereof may be adjusted according to a certain rule.

In the multicolor printing apparatus according to the present invention, the calculation may be performed only between pixels in a direction perpendicular to the printing paper traveling direction.

In the multicolor printing apparatus according to the present invention, the calculation may be performed only for pixels in the direction parallel to the printing paper traveling direction.

According to the multicolor printing apparatus of the present invention, in addition to the printing data itself, the printing data transmitted from the external processing unit is used.
Data indicating the type of print data may be provided, and it may be determined whether or not to perform an operation depending on the type of print data.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The printer 1 includes a print data memory 2, a processor 3, a controller 4, and a print device mechanism 5.

The print data memory 2 stores data to be printed from the external processing unit 6 via the controller 4. The processor 3 operates the print data in the print data memory 2. The controller 4 expands the data from the external processing device 6 in the print data memory 2 or transfers the data stored in the print data memory 2 to the print device mechanism 5,
Make the actual print.

FIGS. 2A to 2D are views showing a part of the print data memory 2. FIG.

FIG. 2A shows the original data. The upper part is the magenta gradation data, and the lower part is the yellow gradation data. Gradation data is maximum 63 to minimum 0
Up to 64 gradations.

FIG. 2B is a diagram showing an example of actual printing using original data. For example, if the printing position of magenta and the printing position of yellow are shifted by one dot, in FIG. 2B, a portion having a low density occurs at a color transition portion surrounded by a dotted line. The original color of the printing medium becomes visible.

FIG. 2C is a diagram showing data obtained by correcting the original data. When the data of the adjacent pixels has a gradation difference of 30 or more, the gradation difference of 1 is calculated from the high gradation pixel data.
/ 4 is subtracted, and 1/4 of the gradation difference is added to the low gradation pixel data. In the original data of magenta, the difference between the tenth pixel and the eleventh pixel is 56. Therefore, the tenth
The pixel data of the pixel is subtracted from 14 which is １ ／ of the gradation difference, and is set to 49. Also, the pixel data of the eleventh pixel is added to 14, which is 1/4 of the gradation difference, to obtain 21. Also,
The difference between the 15th pixel and the 16th pixel is 7. Therefore,
The data of the pair of pixels is not calculated. Next, in the original data of the yellow color, the difference between the tenth pixel and the eleventh pixel is 63. Therefore, the pixel data of the eleventh pixel is subtracted from 16 which is １ ／ of the gradation difference, and is set to 47. Also, the pixel data of the tenth pixel is set to 16
Is added to obtain 16.

FIG. 2D is a diagram showing an example of actual printing using the corrected data. For example, when the printing position of magenta and the printing position of yellow are shifted by one dot, printing is performed using the correction data shown in FIG. 2C, and printing is performed as shown in FIG. 2D. Referring to FIG. 2D, printing is performed at a certain density even at the color transitions indicated by the dotted lines, so that the original color of the printing medium is not seen.

It is to be noted that, when the data of the adjacent pixels has a gradation difference of 30 or more, the pixel data of the high gradation is reduced by 1/4 of the gradation difference to obtain the pixel data of the low gradation. Although 1/4 of the gradation difference is added, the amount of adjustment may be changed. However, the amount of adjustment must be larger than 0 and smaller than 1/2 of the gradation difference. In other words, after the correction,
Make high value data higher than low value data.

Further, in the present embodiment, the case of two colors has been described for the sake of simplicity of description, but the same operation may be performed for many colors.

Further, in the present embodiment, the calculation method is a calculation method unique to each color. However, data of other colors may be corrected in consideration of the color tone and density.

Further, in the present embodiment, only the adjacent pixels are subjected to the calculation, but the adjacent pixels and the peripheral pixels may be subjected to the calculation.

In this embodiment, a one-dimensional method has been described for the sake of simplicity. In other words, a method of correcting only pixels in a direction perpendicular to the printing paper running direction or only pixels in a direction parallel to the printing paper running direction has been described, but two-dimensional correction may be performed.

When the image quality deteriorates when the correction is performed, such as in the case of data including only characters, a flag for determining whether to perform the correction is transmitted from the external arithmetic unit 6 in addition to the print data. , No correction can be performed.

[0028]

As described above, according to the present invention, when print data of adjacent dots has a difference of a certain value or more, the mutual data is adjusted based on a certain rule. Without unnecessary printing, without making the apparatus complicated and expensive, the effect of making the color shift inconspicuous at the color boundary where the color shift becomes conspicuous, and in particular, the ground color of the printing paper is not transparent. Yes.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a part of the print data memory of FIG. 1;

FIG. 3 is a diagram showing a conventional technique.

FIG. 4 is a diagram showing a conventional technique.

FIG. 5 is a diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer 2 Printing data memory 3 Processor 4 Controller 5 Printing apparatus mechanism 6 External processing unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/52 B41J 2/36 B41J 2/525

Claims (7)

(57) [Claims] 1. A printing data memory for storing data to be printed in multiple gradations, a printing apparatus mechanism capable of printing multiple gradations, and a controller for transferring the contents of the printing data memory to the printing apparatus mechanism. in multicolor printing device comprising has a processor for calculating the contents of the print data memory, a plurality of at least two colors each of the color overlaying
For print data of various colors, when the print data of adjacent dots has a difference equal to or greater than a certain value, the processor performs an operation of adjusting the mutual data based on a certain rule. Multicolor printing machine. 2. The print data of adjacent dots, wherein high-value data is subtracted, low-value data is added, and after correction, high-value data is higher than low-value data. Item 8. The multicolor printing apparatus according to Item 1. 3. The multicolor printing apparatus according to claim 1, wherein the calculation method is changed according to the color tone of the dot. 4. The multi-color printing according to claim 1, wherein each of the printing data of the adjacent dots and the printing data of the dots located around the adjacent dots is adjusted based on a predetermined rule. apparatus. 5. The multicolor printing apparatus according to claim 1, wherein said calculation is performed only for pixels in a direction perpendicular to the printing paper traveling direction. 6. The multicolor printing apparatus according to claim 1, wherein the calculation is performed only for pixels in a direction parallel to the printing paper traveling direction. 7. The print data sent from the external arithmetic unit has data indicating the type of print data in addition to the print data itself, and it is determined whether or not to perform an operation depending on the type of print data. 7. The method according to claim 1, wherein
The multicolor printing apparatus according to the above.