Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-08-26
2001-11-27
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S012000, C347S040000
Reexamination Certificate
active
06322197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing method and apparatus, e.g., a color printer, for printing an image on a printing medium.
2. Description of the Related Art
Conventionally, printing apparatuses designed to print images on printing paper and/or cloth by discharging ink from nozzles of printing elements of printheads have been known. Efforts have been made to improve image quality and increase printing speed by various methods.
As such a method, a technique of implementing high-speed printing by reciprocal printing with two-stage printheads arranged in the print media convey direction and improving image quality by using sequential multiscan (SMS) has been proposed (Japanese Patent Laid-Open No. 9-70990).
According to the above prior art, each of the two-stage printheads arranged in the print media convey direction is scanned once to form 1-line pixels (this operation will be referred to as 2-pass printing hereinafter). As shown in
FIG. 22
, therefore, there are four types of half bands (half of the head size) on printing paper, namely half band
1
printed by forward scanning of the first and second heads, half band
2
printed by forward scanning of the first head and backward scanning of the second head, half band
3
printed by backward scanning of the first and second heads, and half band
4
printed by backward scanning of the first head and forward scanning of the second head.
Printing is repeated in a cycle of a set of these four types of half bands, i.e., a total of two bands.
In general, landing states (landing positions, dot sizes, dot shapes, and the like) of dots in forward printing and backward printing differ from each other due to satellites or subdroplets from the heads. The above four types of half bands therefore have their individual characteristics in printing. Since nozzles (four nozzles) for printing half bands are repeatedly combined in units of two bands, half band irregularity occurs.
In addition, to improve image quality and increase printing speed, a plurality of (e.g., two) identical printheads may be disposed in the moving direction of the carriage, and one line (band) may be formed by using a plurality of printheads.
Referring to
FIG. 23
, a 1-line image is formed by 2-pass printing, i.e., reciprocally scanning each of two printheads, spaced apart from each other in the carriage moving direction. In this case, two types of single bands (each corresponding to the head size) are present on printing paper, namely band
1
printed by forward scanning of the first head and forward scanning of the second head, and band
2
printed by backward scanning of the first head and forward scanning of the second head.
Printing is repeated in cycles of one pair of these two types of single bands, i.e., a total of two bands.
In the above case, since landing states of dots in forward printing and backward printing differ from each other due to satellite dots or the like from the printheads, the above two types of bands have their individual characteristics in printing. When combinations (two combinations) of nozzles for printing 1-band images in units of two bands are repeated, 1-band irregularity occurs.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problem in the prior art, and has as its object to provide a printing method which can suppress half band irregularity or 1-band irregularity and implement high-image-quality, high-speed printing, and a printing apparatus using the method.
In order to achieve the above object, according to the present invention, there is provided a printing method for performing printing on a printing medium by using a first printhead having a plurality of printing elements and a second printhead having a plurality of printing elements for performing printing of the same color as that performed by the first printhead, comprising:
the first print step of scanning the first printhead;
the second print step of scanning the first printhead in a direction opposite to the scanning direction in the first print step;
the third print step of scanning the second printhead;
the fourth print step of scanning the second printhead in a direction opposite to the scanning direction in the third print step; and
the convey step of conveying the printing medium during the first, second, third, and fourth print steps,
wherein an image in a predetermined area within a band formed by one scanning operation by all the printing elements of the first or second printhead is formed through the first to fourth print steps.
According to the present invention, there is provided another printing method of performing printing on a printing medium by reciprocally scanning a first printhead having a plurality of printing elements and a second printhead having a plurality of printing elements for performing printing of the same color as that performed by the first printhead, comprising:
the distribution step of distributing image data printed in a predetermined area within a band formed by one scanning operation by all the printing elements of the first or second printhead, of all image data to be printed on the printing medium, as first data to be printed by the first printhead and second data to be printed by the second printhead; and
the extraction step of extracting third and fourth data respectively used for forward printing and backward printing by the first printhead from the first data, and fifth and sixth data respectively used for forward printing and backward printing by the second printhead from the second data.
In addition, according to the present invention, there is provided a printing apparatus for performing printing on a printing medium by reciprocally scanning a first printhead having a plurality of printing elements and a second printhead having a plurality of printing elements for performing printing of the same color as that performed by the first printhead, comprising:
distribution means for distributing all image data to be printed on the printing medium as first data to be printed by the first printhead and second data to be printed by the second printhead; and
extraction means for extracting third and fourth data respectively used for forward printing and backward printing by the first printhead from the first data, and fifth and sixth data respectively used for forward printing and backward printing by the second printhead from the second data,
wherein 4-pass printing is performed to form an image in a predetermined area within a band formed by one scanning operation by all the printing elements of the first or second printhead by printing the third, fourth, fifth, and sixth data.
In this case, when all the image data are divided into print data and non-print data, it is preferable that the distribution means uniformly distribute the print data as the first and second data.
In addition, preferably, the extraction means extracts data by using a first mask in which areas to be allocated to the third and fourth data of the first data are predetermined and a second mask in which areas to be allocated to the fifth and sixth data of the second data are predetermined.
Furthermore, preferably, the extraction means converts image data in an area allocated to the fourth data into non-print data on the basis of the first mask when extracting the third data from the first data, converts image data in an area allocated to the third data into non-print data on the basis of the first mask when extracting the fourth data from the first data, converts image data in an area allocated to the sixth data into non-print data on the basis of the second mask when extracting the fifth data from the second data, and converts image data in an area allocated to the fifth data into non-print data on the basis of the second mask when extracting the sixth data from the second data.
Preferably, the extraction means reads out no image data in an area allocated to the fourth data on the basis of the first mask when extracting the third data from the first data, reads out no imag
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Le N.
Nguyen Lamson D.
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