Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-03
2001-02-06
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S043000
Reexamination Certificate
active
06183062
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to liquid ink recording devices using two or more different color inks. More particularly, the present invention is directed to maintaining edge quality at the interface of printed areas and non-printed areas.
Liquid ink printers of the type often referred to as continuous stream or as drop-on-demand, such as piezoelectric, acoustic, phase change wax-based or thermal, employ at least one printhead from which droplets of ink are directed towards a recording sheet. Within the printhead, the ink is contained in a plurality of channels. Power pulses cause the droplets of ink to be expelled as required from orifices or nozzles at the end of the channels.
Liquid ink printers including ink jet printers deposit black and/or colored liquid inks which tend to spread when the ink is deposited on paper as a drop, spot, or dot. A problem of liquid ink printers is that the liquid inks used have a finite drying time, which tends to be somewhat longer than desired. Bleeding tends to occur when the drops are placed next to each other in a consecutive order or in a cluster of dots within a short time. Bleeding, spreading, and feathering causes print quality degradation including color shift, reduction in edge sharpness and solid area mottle which includes density variations in said areas due to puddling of inks. Intercolor bleeding occurs when ink from one color area blends into or bleeds with ink from another color area. Intercolor bleeding is often most pronounced where an area of black ink (relatively slow drying) adjoins an area of color ink (relatively fast drying); however, intercolor bleeding can occur at the interface between areas of any color inks having substantially different properties such as dry time or permeability.
Various methods have been proposed to increase edge sharpness and to reduce intercolor bleeding. Some of the proposed methods include replacing slow drying black ink with a process or composite black formed by combing fast drying color inks; under-printing a portion of the slow drying black ink with a color ink, use a fast drying black ink, and using both fast dry and slow dry black ink. While all of the proposed methods reduce intercolor bleeding to some degree, they all have one or more drawbacks that effect printer performance and/or image quality.
For example, using a fast dry ink in place of a slow drying black ink results in a reduced quality of black reproduction as current fast drying black inks have lower image quality than slow drying black inks. Additionally, fast drying black inks typically result in fuzzy edges in black areas next to non-printed areas. The use fast drying black ink at an interface and slow drying black ink for interior regions can eliminate lower image quality associated with fast drying black inks, but increases the cost and complexity of printer design by requiring a fifth ink in addition to the cyan, magenta, yellow and slow drying black ink. Similarly, replacing slow drying black ink with a process black (composite black) generated from fast drying color inks typically results in a reduced quality of black reproduction resulting in a lower image quality than the use of slow drying black ink. Additionally, the use of process black increases the amount of ink deposited on the print medium, increases dry time and increase the time to print a document. Furthermore, the use of additional ink may not be suitable for print medium such as transparencies and some types of paper which is not very absorbent. Under-printing a portion of the slow drying black ink with a color ink can be used to reduce intercolor bleeding; however, under-printing increases the amount of ink on the print medium. Moreover, printing color under black often results in the thickening or blurring of edges particularly along edges between printed and non-printed areas.
SUMMARY OF THE INVENTION
One aspect of the present invention is a process for processing color image data to maintain edge quality in an image recorded on a receiving medium. The method includes receiving color image data comprising a plurality of color planes, the color planes including at least one black plane and at least one non-black plane, wherein each color plane comprises an array of separation pixels, each separation pixel having at least three states, a first state corresponding to depositing no ink, a second state corresponding to depositing one ink drop, and a third state corresponding to depositing more than one ink drop; identifying an interface between an black area and a non-printed area; defining an N-pixel wide border in the black area; and modifying the color image data corresponding to the N-pixel wide border to set substantially all the separation pixels in the black plane to a selected pixel state.
Another aspect of the present invention is method of processing color image data for printing on an inkjet printer to maintain edge quality in an image recorded on a receiving medium. The method comprises: receiving a target pixel comprising multiple separation pixels, each separation being associated with a separate color plane and having at least three states, a first state corresponding to depositing no ink, a second state corresponding to depositing one ink drop, and a third state corresponding to depositing more than one ink drop; determining if the target pixel is within a black border region near a black
on-printed interface; and if so, setting the separation pixel associated with a black color plane to a selected black pixel state.
A third aspect of the present invention is a device for processing color image data to maintain edge quality in an image recorded on a receiving medium. The device includes a black window filter, a pixel identification circuit and a pixel identification circuit. The black window filter is connected to receive a first set of pixels including a target pixel comprising multiple separation pixels, each separation being associated with a separate color plane and having at least three states, a first state corresponding to depositing no ink, a second state corresponding to depositing one ink drop, and a third state corresponding to depositing more than one ink drop, and generate a black statistics signal. The pixel identification circuit receives the black statistics signal and generates a pixel identification signal indicating whether the target pixel is within a black border region near a black
on-printed interface. The pixel identification circuit receives the pixel identification signal and filters the target pixel to set the separation pixel associated with a black color plane to a selected black pixel state.
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Curtis Christopher R.
Hull Virgil Joseph
Smith Glenn K.
Torpey Peter A.
Eipert William
Nguyen Thinh
Xerox Corporation
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