Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-10-30
2001-09-25
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06293657
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to ink-jet printers/plotters, and more particularly to techniques for stopping and restarting printing operations in mid-plot while minimizing printing artifacts resulting from stopping in mid-plot.
BACKGROUND OF THE INVENTION
Swath printers/plotters are in widespread use today for printing many types of images. A printing system suitable for a printer is described in U.S. Pat. No. 5,745,137, which employs off-carriage ink reservoirs connected to on-carriage print cartridges through flexible tubing. The off-carriage reservoirs continuously replenish the supply of ink in the internal reservoirs of the on-carriage print cartridges (or “printheads” or “pens”), and maintain the back pressure in a range which results in high print quality. While this system has many advantages, there are some applications in which the relatively permanent connection of the off-carriage and on-carriage reservoirs via tubing is undesirable.
An ink delivery system (IDS) for printers has been developed, wherein the on-carriage reservoir of the print-head is only intermittently connected to the off-carriage reservoir to “take a gulp” and is then disconnected from the off-carriage reservoir. No tubing permanently connecting the on-carriage and off-carriage elements is needed. The above-referenced related applications describe certain features of this “take a gulp” ink delivery system.
When an inkjet printer starts a print using a multi-pass print mode, the top of the page is printed with just a few nozzles of the printheads, the print medium is advanced a short distance, a few more nozzles are printed, and the print medium is again advanced a short distance, and so on. When the printer is printing normally during a print or plot using a multi-pass print mode, there are several partially formed swaths (groups of rows of pixels) with some pixels printed, and others not yet printed. At the end of a plot, the printer completes all pixels of all rows before stopping.
The take-a-gulp system as well as other large scale plotters can be employed to print large color images, wherein significant volumes of the colored inks can be used from the on-carriage reservoirs during a given print. The system includes the capability of tracking the ink volume spent from one or more of the on-board ink reservoirs and thus providing a measure of the ink remaining, and detecting when a reservoir needs refilling. If this occurs while printing, and the system were to invoke a refill operation as if doing a normal pen servicing, the carriage would be moved to the service/refill station, even though the plot is not completed, and the refill operation performed. A problem is that this interruption in printing leaves the image drying for a relatively long period of time, perhaps several minutes, before printing is resumed to complete the plot. In some print media, this action creates an arti-fact, a visible horizontal band all across the page, at the area at which printing was interrupted for the refill. Additionally, the printheads cool off during this pause, and water evaporates from the printhead nozzles, which can result in different print performance when printing resumes.
There was no solution to this problem. In other platforms, printing was continued until the cartridge ran out of ink and then the machine canceled the plot. Other possible outcomes included a very visible artifact resulting from printing interruption, or not completing the print, or printing the image with a white gap and perhaps missing some information.
It would therefore represent an advance in the art to provide a technique for reducing artifacts resulting from mid-plot-pausing.
SUMMARY OF THE INVENTION
A technique is described for carrying out a mid-plot pause, e.g. to perform a refill operation after the printer has determined that the ink level of an internal reservoir of a printhead is low. The system can invoke a refill operation as if doing a normal pen servicing, which entails moving the carriage to the service/refill station, even though the plot is not completed, and performing a refill operation. This type of refill operation will sometimes be referred to herein as an “interleaved” refill. This interruption in printing leaves the image drying for a relatively long period of time, perhaps several minutes. In some medias this action creates an artifact, a visible horizontal band all across the page.
If the printer is stopped mid-plot, after printing a given pass, the image will appear as faded out due to incomplete printing over a distance corresponding to the length of the printhead nozzle array. If this partially printed area is then printed on after a delay, say for refilling, easily visible artifacts typically occur.
By simulating an “end of plot” behavior when going to refill, and commencing printing again after refilling as if it was a “start of plot,” the band artifact problem can be avoided. The simulated “end of plot” behavior is to “finish” printing through a specified row of the image, completing all pixels in a normal manner, but not printing any pixels below this row. This results in an image that is completely printed up to a defined line (row), and so there will be totally clear (no dots) medium next to a fully printed image portion.
The “start of plot” behavior entails restarting the printing of the image after a mid-plot pause,. e.g. to perform a refill, with the printhead positioned mostly over the already printed portion of the image, and using only a few nozzles (just as at the top of the page) printing a pass, then advancing the paper a short distance, printing a pass using a few more nozzles, and so on. Thus, printing is resumed after a mid-plot pause without losing image information or the physical position on the paper, so the print can be completed with little or no visible artifact.
When the print medium is loaded into the printer, the user typically selects a medium type. Based on the type selected, the printhead ink type and the print quality selected, different techniques can be applied if a mid-plot refill is required. It can happen on some types of print media that using the simulated “end of plot” and “start of plot” technique creates a white line because of the dry ink repelling wet ink. To minimize this, the algorithm can be adapted to select the type of refill operation in dependence on variables, including the media type, wherein an interlaced refill scheme can be employed instead of an “end of plot” technique. The interlaced scheme is a technique wherein the multi-pass printing is stopped at the end of a printhead pass with partially formed swaths on the print medium, the refill operation is performed, and the printing is resumed almost as if no delay had occurred. Also for some print qualities on the same media, it may be more convenient to use an end of plot scheme or an interlaced one. With all these variables, a matrix of medias and print qualities is configured for choosing the algorithm to use. Alternatively, the user can directly select the type of refill technique through a front panel menu system.
Thus, in accordance with an aspect of the invention, a method is described of pausing and resuming printing operations. The method reduces print artifacts resulting from pausing and resuming the printing in mid-plot, and comprises the following steps:
determining a pause row location at which printing is to be paused;
completing the printing of all rows and all pixels from commencement of printing through the row location, and wherein no pixels in rows immediately following the row location are printed, wherein printing is completed on the image up to the row location, and the print medium is free of any printing next to the row location;
pausing the printing for a time interval; and
resuming printing at a resume row location immediately following the pause row location to print only rows following the pause row, wherein wet ink is not applied to locations printed prior to the pausing.
An accordance with a further aspect of the invention, a method of pau
Donovan David H.
Garcia Javier Salvador Lagares
Hewlett--Packard Company
Le N.
Nguyen Michael
LandOfFree
Mid plot refill technique for large scale printers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mid plot refill technique for large scale printers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mid plot refill technique for large scale printers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2506224