Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-10-26
2001-11-13
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S017000
Reexamination Certificate
active
06315379
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to ink jet printing systems and methods.
2. Description of Related Art
Continuous stream or drop-on-demand liquid ink printers, such as piezoelectric, acoustic, phase change wax-based or thermal printers, have at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in at least one channel, or preferably 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.
In a thermal ink-jet printer, the power pulse is usually produced by a heater transducer or resistor, typically associated with one of the channels. Each heater transducer or resistor is individually addressable to heat and vaporize ink in one of the plurality of channels.
The ink jet printhead may be incorporated into either a carriage type printer, a partial-width-array type printer, or a page-width type printer. The carriage type printer typically has a relative small printhead containing the ink channels and nozzles. The printhead can be sealingly attached to a disposable ink supply cartridge. The combined printhead and cartridge assembly is attached to a carriage, which is reciprocated to print one swath of information at a time on a stationary recording medium, such as paper or a transparency. Each swath has a width equal to the length of a column of nozzles. After each swath is printed, the recording medium is stepped a distance equal to the height of the printed swath or a portion of the swath, so that the next printed swath is contiguous or overlapping with the previously printed swath. This procedure is repeated until the entire page is printed.
The page-width printer includes a stationary printhead having a length sufficient to print across the width or length of a sheet of recording medium at a time. The recording medium is continually moved past the page width printhead in a direction substantially normal to the printhead length and at a constant or varying speed during the printing process. A page width ink-jet printer is described, for instance, in U.S. Pat. No. 5,192,959.
Many liquid inks, and particularly those used in thermal ink jet printing, include a colorant or dye and a liquid, which is typically an aqueous liquid vehicle, such as water and/or a low vapor pressure solvent. The ink is deposited on the recording medium to form an image in the form of text, graphics and/or pictures. Once deposited, the liquid component is removed from the ink and the recording medium to fix the colorant to the recording medium by either natural air drying or by active drying. In natural air drying, the liquid component of the ink deposited on the recording medium is allowed to evaporate and to penetrate into the substrate naturally without mechanical assistance. In active drying, the recording medium is exposed to heat energy of various types, which can include infrared heating, conductive heating and heating by microwave energy. Active drying of the image can occur either during the imaging process or after the image has been made on the recording medium.
Natural air drying and active dryer each have an operating range. That is, natural air drying and active dryer are not able to dry more than a certain amount of ink per unit of time, called the “ink drying rate”. The ink drying rate depends from the humidity and the temperature of the ambient air.
SUMMARY OF THE INVENTION
The pixel printing rate of a document is defined by the number of pixels to be printed during a unit of time. The pixel printing rate is proportional to the area coverage of each sheet of recording medium multiplied by the speed of the printer, i.e., the number of pages printed per minute.
In most printers, the ink drying rate of a printer is typically less than the maximum pixel printing rate that the printer can reach, because most printed documents, and particularly those that do not incorporate photographs or other graphics elements, have an area coverage less than about five percent. Even documents including very high density photographs have an area coverage generally less than about fifty percent.
However, when the pixel printing rate exceeds the ink drying rate on a previous printed document, some ink may remain liquid on this previous printed document when the next document is printed and, thus, the next printed document may be spotted by the liquid ink remaining on the previous document.
In thermal ink jet printers, the amount of power delivered to the heater transducers or resistors incorporated in the printhead is dependent on the rate at which pixels are printed, which is in turn a function of the area coverage and the process speed. If the amount of power of the power supply exceeds a threshold amount, the power supply could become damaged. This damage can occur due to various physical effects, such as temperature, current density, etc. Much of the power delivered to the resistors remains in the printhead after the pixel is printed. This power generates heat, which increases the temperature of the printhead. In order to maintain a temperature of the printhead in an operating range of temperatures, the excess heat must be removed. Otherwise, the printhead or the quality of the printed documents could deteriorate.
Accordingly, the design of the print head is affected by the maximum pixel printing rate. In the same way, the cooling system, the driving cost, the complexity of the printer and its size are affected by the maximum pixel printing rate.
In a variable speed architecture, a printer controller monitors the pixel printing rate. When the pixel printing rate exceeds a specified threshold, the printer controller reduces the process speed. Thus, the pixel printing rate remains below the specified threshold regardless of the area coverage of the images to be printed.
This invention provides systems and methods for printing documents at full speed, regardless of the pixel printing rate of the image to be printed.
In a first exemplary embodiment of the systems and methods according to this invention, when an image area coverage exceeds a predetermined threshold corresponding to a predetermined maximum pixel printing rate, the printed image area coverage is reduced relative to the input image area coverage, to obtain a pixel printing rate that is less than the maximum pixel printing rate.
In a second exemplary embodiment of the systems and methods according to this invention, a printing mode is selected between a full-speed variable density printing mode and a full-density variable speed printing mode. In the full-speed variable density printing mode, when the image area coverage exceeds a predetermined threshold corresponding to a predetermined maximum pixel printing rate, a selected printing mode is performed.
According to exemplary embodiments of the systems and methods according to this invention, a printhead temperature sensor and/or an ambient humidity sensor can be provided to define the predetermined threshold.
According to other exemplary embodiments of the systems and methods according to this invention, the image area coverage compared to the threshold is the image area coverage of one sheet of recording medium to be printed.
According to other exemplary embodiments of the systems and methods according to this invention, a ratio p
of pixel to be dropped out is determined according to the image area coverage and p pixels out of n pixels to be printed are drop out of the image to be printed.
According to other exemplary embodiments of the systems and methods according to this invention, the resolution used by the printer driver is reduced when the image area coverage is higher than the predetermined threshold.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of the apparatus/systems and methods according to this invention.
REFERENCES:
patent: 5107276 (1992-04-01), Kneezel et al.
patent: 5917519 (1999-06-01),
Adams Jerry F.
Audi Anthony E.
Bauer Gary K.
Brockman Thomas J.
Collier Bruce A.
Oliff & Berridg,e PLC
Vo Anh T. N.
Xerox Corporation
LandOfFree
Systems and methods for selectively blocking image data does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Systems and methods for selectively blocking image data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Systems and methods for selectively blocking image data will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597224