Systems and methods for generating high addressability images

Details Systems and methods for generating high addressability images Systems and methods for generating high addressability images

1999-06-30

2001-12-04

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C358S001200, C358S448000

Reexamination Certificate

active

06325487

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to systems and methods for generating high addressability images.
2. Description of Related Art
The pixels in a binary image may be either on or off, i.e., black or white, respectively. In particular, the binary image may be a binary image possessing both highlights and shadows and having normal addressability. However, various devices have the capability to generate a high addressability image. A high addressability binary image is an image created by a device such that the spatial addressability of the image pixel by the device is finer than the size of the writing spot of that device. High addressability also often refers to an addressability resolution in a first direction that is finer than the spatial addressability resolution in a second direction that is, for example, perpendicular to the first direction. High addressability data can be used to render edges in text and line art regions at a high spatial precision in the high addressability direction. High addressability data can also be used in halftone regions to provide additional spatial resolution in the high addressability direction.
Illustratively,
FIG. 1
is a diagram showing a high addressability pixel grid. As shown in
FIG. 1
, the spatial addressability of the pixels in the horizontal direction, i.e., the fast scan direction, is finer than in the vertical direction, i.e., the slow scan or process direction.
FIG. 1
illustrates an image having a high addressability of 4. That is, each nominal “pixel”
114
contains four “subpixels”
124
. This distinction between a pixel
114
and a subpixel
124
is used throughout this application. Images may have various other high addressability values, such as an addressability of 8. A high addressability image may be referred to as an “anamorphic” image since the high addressability image possesses different spatial resolutions in mutually perpendicular directions. In contrast, an “isomorphic” image possesses the same spatial resolution in mutually perpendicular directions.
SUMMARY OF THE INVENTION
However, problems occur in conventional methods when inputting and manipulating images, and subsequently reproducing or printing high addressability images. In particular, problems occur in the conventional methods when printing high addressability binary images or image regions, such as images possessing shadows and highlights, for example. The image may be black and white only, or in color.
Random access ink jet printers, such as those disclosed in U.S. Pat. No. 5,675,365 to Becerra et al., allow great flexibility in the sequence in which individual pixels are printed or fired. This occurs by allowing the individual ink ejections to be scheduled, rather than addressing them in a fixed order at a fixed clock speed. This scheduling allows more flexibility in which particular pixels may be printed to achieve a desired image on a recording medium using a choice of pixel firing patterns.
In a conventional ink ejection device, such as those disclosed in the 365 patent, an individual ink ejector is addressed at some frequency f. That ink ejector is either fired or not fired each time it is addressed. However, such an ink ejection device actually addresses the ink ejectors at a rate that is much faster than f, i.e., at the clock rate. These known devices provide flexible addressing and allow an ejector to be fired at any clock cycle.
However, there are constraints on the degree of flexibility. One constraint is that an individual ink ejector can not be repeatedly fired too soon or the ink ejector will not have time to refill between firing. Another constraint is that only a certain number of ink ejectors can be fired at a time due to operation limitations of the printing device relating to the ink supply to the ink ejectors. However, it has been observed that neither of these constraints greatly limits the flexibility of current known ink ejection devices.
Illustratively, neither constraint need be violated for a known ink ejection device to print full black. For known devices, such as those disclosed in the 365 patent, to print gray, the ink ejection print head only needs to lower the frequency at which a given ink ejector is fired from that necessary for full black.
However, there are various problems with known devices in printing high addressability images. One problem occurs when printing high addressability images having highlights. When printing such images, a substantial amount of processing time is spent trying to optimize the highlights. However, in highlights, there is little advantage to high addressability. The second problem observed with conventional methods is that the extension of such conventional methods to print color high addressability images is difficult.
Further, other known methods of printing high addressability images interpolate between pixel values, and in particular between subpixel values in the high addressability image. Using this interpolation, the known methods determine which subpixels are turned on and which subpixels are left off. This approach takes advantage of the ability of known printers to start or stop printing at a fractional pixel. In such printing, it should be appreciated that there is a practical constraint on both the smallest image pixel size and the smallest gap size between printing.
However, this approach involving printing a fractional pixel is not possible in an ink jet printer. Known ink jet printer techniques allow a determination of which subpixel the drop is printed in. However, known ink jet printer technology cannot print a fractional drop, i.e., a part of a drop. Accordingly, the conventional processes have various problems associated with them.
Accordingly, this invention provides systems and methods that generate a high addressability image using an ink ejection image forming device.
This invention separately provides systems and methods that print a high addressability binary image using random access ink ejecting printing techniques.
This invention separately provides systems and methods that print a high addressability binary image, where the number of drops printed in each pixel is at least one but less than the addressability of the apparatus used to print the image.
This invention separately provides systems and methods for printing high addressability images which are easily extended to color.
This invention separately provides systems and methods for directly determining the address of where a pixel prints and thus eliminating the need to convert a high addressability binary file into a format needed by the printhead.
This invention separately provides systems and methods for printing high addressability images that reduce any introduced image defects in the printed image.
This invention separately provides systems and methods that use information of neighboring pixel values to print a high addressability pixel group.
This invention separately provides systems and methods for performing an error diffusion process for thermal ink jet printing.
This invention separately provides systems and methods for performing fast printing that does not require substantial additional processing time over regular error diffusion processes.
This invention separately provides systems and methods for automatically compressing outputted data into a format needed for known random access ink ejection chip architectures.
This invention separately provides systems and methods for printing high addressability pixels in an image in a manner such that images including highlights may be printed while limiting the presence of artifacts, such as worms, in the image.
The term “worms” refers to artifacts generated by error diffusion in highlight (and shadow) regions, in which marks (or unmarked areas, in shadow regions) are not distributed equally in two dimensions, such that curved lines are visible in the error diffusion region.
The exemplary embodiments of the systems and methods of the invention generate improved high addressability images. In accordance with th

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