Printing apparatus and method

Details Printing apparatus and method Printing apparatus and method

2001-07-17

2003-05-06

Nguyen, Judy (Department: 2853)

Incremental printing of symbolic information

Ink jet

Controller

C358S003010

Reexamination Certificate

active

06557964

ABSTRACT:

This application is based on Patent Application No. 2000-216694 filed Jul. 17, 2000 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing apparatus and method, and in particular, to a printing apparatus and method suitable for use in ink jet printing systems.
2. Description of the Related Art
Serial-scanning printing apparatuses that perform printing operations while scanning a print head on printing medium have been adapted to various image printing applications. In particular, ink jet printing apparatuses have been spreading rapidly due to their recently increased resolution and recently improved color printing function, which lead to an improved image grade. The serial-scanning printing apparatuses sequentially print images on printing medium by repeating a printing operation of printing an image on a printing medium while moving a print head in a main-scanning direction and a transporting operation of transporting the printing medium in a sub-scanning direction.
The serial-scanning ink jet printing apparatuses use, as a print head, a multi-nozzle head having a plurality of ejection ports integrated and arranged therein and constituting nozzles capable of ejecting ink droplets. Images can be printed with a higher resolution by increasing the integration density of the ejection ports and reducing the amount of ink ejected per dot. Further, for high-quality image printing equivalent to silver salt photographing, many techniques have been developed; for example, in addition to four basic color inks (cyan, magenta, yellow, and black), lighter-color inks of lower densities are provided, so that a total of six color inks (cyan, magenta, yellow, black, light cyan, and light magenta) are used for printing. Moreover, to avoid a decrease in printing speed associated with the increased image quality, techniques have been employed which increase the number of printing elements deployed in an arrangement including the ejection ports, increase the driving frequency for the print head, or enable bi-directional printing in which a printing operation is performed when the print head is scanned in either direction. As a result, the high throughput has been improved.
For these serial-scanning ink jet printing apparatuses, various proposals have been made for the construction of the print head and the printing method in order to deal with higher-resolution image printing.
FIGS. 11
to
13
are illustrations of an example of a construction of an ink jet print head H as a multi-nozzle head which includes nozzles arranged at a higher density to achieve high-density image printing. For the multi-nozzle head, a one-row nozzle arrangement in which ejection ports are arranged in a row has a limited nozzle arrangement density due to a manufacturing method used. Thus, in the print head H shown in
FIG. 11
, a plurality of ejection ports P capable of ejecting ink are formed so as to constitute two rows (hereafter also referred to as “nozzle rows”) L
1
and L
2
. The nozzle rows L
1
and L
2
extend in the sub-scanning direction shown by an arrow B in which printing medium is transported, and the ejection ports P are arranged at a predetermined pitch Py in each of the nozzle rows L
1
and L
2
. An arrow X indicates a main-scanning direction in which the print head H reciprocates. The ejection ports P in the nozzle row L
1
are offset from the ejection ports P in the nozzle row L
2
by half a pitch (Py/2) in the sub-scanning direction. This serves to achieve a resolution twice as high as that achieved by single nozzle row. If, for example, six color inks are used to print image, six print heads H for ejecting the corresponding inks are provided in the sub-scanning direction. And, for each of the print heads H, timings for ejecting the ink from the ejection ports P in the nozzle rows L
1
and L
2
are adjusted. When image is thus printed using the one color ink from the two nozzle rows L
1
and L
2
, color image of a double resolution can be printed compared to the one color ink from the one nozzle row.
On the other hand, the printing resolution of the printing apparatus does not always equal the resolution of image data input to the printing apparatus from a host apparatus (the latter resolution is hereafter referred to as an “input resolution”). The recent printing apparatuses can perform printing operations corresponding to a plurality of input resolutions. If, for example, the printing apparatus has a printing resolution of 1,200 dpi (dot/inch), the processing time and data transfer time of the host apparatus can be reduced when it processes image data at a resolution of 300 ppi (pixel/inch) and transfers it to the printing apparatus. If the host apparatus processes the image data at a resolution of 1,200 ppi correspondingly to the printing resolution of the printing apparatus, and transfers the data to the printing apparatus, then the host apparatus is overloaded. If the host apparatus processes the image data at a resolution of 300 ppi, one-fourth of 1,200 ppi, and transfers it to the printing apparatus, then the printing apparatus can print the image data in a printing area of 4×4 pixels while applying gradation thereto.
Such a printing method is described, for example, in Japanese Patent Application Laid-open No. 9-46522 (1997).
FIG. 15
is an illustration of an example of that printing method. In the example in
FIG. 15
, the printing apparatus prints an image at a resolution of 600 dpi on the basis of image data of 300 ppi resolution transferred from the host apparatus. If the image data of 300 ppi input resolution is printed with the resolution unchanged, the printing resolution is 300 dpi. Thus, the example in
FIG. 15
also corresponds to the case in which the printing apparatus prints an image at a resolution of 600 dpi on the basis of image data of 300 ppi resolution transferred from the host apparatus.
The printing apparatus uses an arrangement pattern (hereafter referred to as a “dot arrangement pattern”) of dots D in a printing area of 2×2 pixels to achieve printing with five-value gradation from “level 0” to “level 4”, as denoted by reference signs (a) to (e) in
FIG. 15. A
plurality of dot arrangement patterns are used for the “level 1”, “level 2”, and “level 3”. Japanese Patent Application Laid-open No. 9-46522 (1997) describes the sequential and random use of such a plurality of dot arrangement patterns. As denoted by reference signs (b), (c), and (d) in
FIG. 15
, the arrangements of the dots D for expressing the “level 1”, “level 2”, and “level 3” gradations are not fixed. Thus, preventing the movement of the inks on a printing medium, for example, pseudo contours resulting from a pseudo half toning process or what is called “sweep-up phenomenon” occurring at edge portions of the image. Further, the frequency of the use of the print head nozzles can be leveled out.
Such a printing method is particularly effective on printing apparatuses of a high printing resolution. For high-quality image printing equivalent to photographing, the input resolution need not exceed a visually perceived range. As long as an input resolution of about 600 dpi is obtained, increasing the gradation of pixels is more effective than further increasing the input resolution. Moreover, smooth and less granular images can be printed by using the above described six color inks including the light color inks to improve the gradation.
Further, as the printing density increases with the resolution, the throughput may decrease. To prevent this, what is called a column thinning printing system or the like has been proposed in addition to the above described increase in the number of nozzles, increase in the driving frequency for the print heads, and proposal for bi-directional printing.
Next, the column thinning printing system will be described. Typically, in the serial-scanning ink jet printing apparatus, the speed at which a carriage with print heads mounted thereon moves in the main-scan

Affiliated with

Also associated with

Rating

Printing apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Printing apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Printing apparatus and method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3078981