Abstract: A method and apparatus for reducing intercolor bleed using pixel spot size control to improve print quality is provided. The method includes printing pixels having a first spot size in an image region having a boundary between a first color portion and a second color portion of the image by ejecting first sized ink drops from the printhead nozzles, and printing border pixels having spot sizes smaller than the first spot size in the image region by ejecting smaller ink drops from the printhead nozzles, wherein the smaller ink drops are smaller than the first sized ink drops. A printing system is provided having means for printing pixels in the region having the first spot size and means for printing border pixels having spot sizes smaller than the first spot size.

Abstract: An improved temperature compensation method is disclosed in which a temperature sensing thermistor is formed on a substrate whose temperature is to be series of fractional thermistors which are selectively shorted out during a manufacturing process to provide a compensation for manufacturing variabilities of the temperature coefficient of resistance of the thermistor.

Abstract: Individual printheads are joined together in a manner to provide improved alignment and registration. The multiple printhead assembly is then installed and removed from the printer as a single unit. According to a preferred method of forming the assembly, individual printheads are temporarily mounted on a holddown plate. The location and position of the printheads is monitored and a fast-cure adhesive used to monolithically join the individual printheads together as a unitary assembly. Once the adhesive is cured, the temporary securing of the individual printheads is removed and the entire assembly removed as a single unit from the holddown plate.

Abstract: An ink jet printer has a temperature sensor as a permanent part thereof to measure the temperature of printheads which are an integral part of a replaceable printhead cartridge assembly. The temperature sensor is a part of the maintenance station and senses the temperature of the printheads each time the printhead enters the maintenance station. In the preferred embodiment, the temperature sensor is spring-loaded and is located at a printhead spitting location between fixed wiper blades and the capping location in the maintenance station, so that temperature is sensed each time the printhead enters and leaves the maintenance station to eject nozzle cleaning droplets onto a collection surface at the spitting location to clean the printhead nozzle face by the wiper blades, or to cap the printhead nozzles. To facilitate good thermal contact, a recess is provided in the heat sink upon which the printhead resides for entry by the spring-loaded temperature sensor.

Abstract: An ink jet printer has a temperature sensor as a permanent part thereof. The temperature sensor is mounted on the translatable carriage of the printer. A replaceable printhead cartridge having a printhead bonded to a heat sink is installed on the translatable carriage. Once the printhead cartridge is installed on the translatable carriage, the temperature sensor is placed into intimate contact with printhead'heat sink, so that the temperature sensor moves with the printhead and provides continual temperature measurement.

Abstract: A power control system in a thermal ink-jet printer facilitates practically instantaneous voltage changes to a heating element. A first set of selectably-actuable voltage lines is operatively connected in parallel to a first terminal of the heating element, each line having associated therewith a predetermined voltage output. A second set of selectably-actuable voltage lines is operatively connected in parallel to a second terminal of the heating element, each line having associated therewith a predetermined voltage output. One of the first set of selectably-actuable voltage lines and one of the second set of selectably-actuable voltage lines are activated as required.

Abstract: A control system for a printer having at least one heating element for producing spots applies one of a plurality of voltage levels to at least one heating element disposed on a printhead. A voltage supply supplies a voltage to a first one of a plurality of switches connected in series with a last one of the switches being connected to the at least one heating element. At least one of the switches defines a first path and a second path having different voltage drops. A controller coupled to the plurality of switches selectively actuates the switches to apply one of a plurality of predetermined voltages to the at least one heating element.

Abstract: A thermal ink-jet printhead adapted to emit ink onto a print sheet is automatically adjusted. The printhead is caused to emit ink onto a sheet in a manner consistent with an image of a first density, and then substantially immediately caused to emit ink in the form of a first test pattern on the sheet. The density of the first test pattern on the sheet is measured. The printhead is caused to emit ink onto the sheet in a manner consistent with an image of a second density, and then substantially immediately caused to emit ink in the form of a second test pattern on the sheet. The density of the second test pattern on the sheet is measured. The densities of the first test pattern and the second test pattern are correlated with a function relating a characteristic of an image printed with the printhead to a temperature of the printhead.

Abstract: Data relating to the performance of an individual ink-jet printhead is stored in an electrically-readable form on a silicon substrate forming an essential part of the printhead. A template of electrically-detectable structure is created on the substrate at manufacture, and then portions of the structure are removed in accordance with the data desired to be stored. In one embodiment, the digital performance data may be encoded and also read out in serial form using a shift register on the chip.

Abstract: An apparatus and method compensates for a voltage drop of electrical pulse signals selectively applied to a plurality of heater elements on a printhead of an ink jet printing device. A number of heater elements to be pulsed at a given time is determined and a time duration of each of the pulse signals is selected based on information including the determined number of heater elements to be pulsed. In another aspect, the position on the printhead of the heater elements to be pulsed is determined and the time duration of the pulse signals is selected further based on the determined position. By varying the time duration of the pulse signals applied to the heater elements, a voltage drop across the heater elements due to the number of heater elements simultaneously pulsed and/or the position of the heater elements on the printhead is compensated for, maintaining reliable jetting performance while minimizing the voltage by which operating printing voltage needs to exceed the threshold printing voltage.

Abstract: A thermal ink jet printhead is controlled to minimize missing droplets at elevated operating temperatures by varying the voltage and pulse width applied to the heater element that causes droplets to be formed and ejected. Increasing the applied voltage reduces the size of the formed droplets. At increased operating temperatures, smaller droplets minimize the introduction of air into the nozzles of the printhead upon ejection. Minimizing the introduction of air eliminates printhead misfirings and causes more consistent jetting of the ink droplets.

Abstract: A thermal ink-jet printhead comprises a substrate having a plurality of heating elements defined thereon. A thermistor, disposed on the substrate, includes a conductor loop which does not encompass the heating elements on the substrate. The configuration of the thermistor significantly reduces both electromagnetic and capacitance interference caused by the heating elements.

Abstract: A system controls an ink jet printing apparatus for propelling ink jet droplets on demand from a printhead having a plurality of drop ejectors. In the printhead, each ejector includes a heating element actuable in response to electrical input signals, each input signal having an amplitude and a time duration, selectably applied to the heating element to produce a temporary vapor bubble and cause a quantity of ink to be emitted for the creation of a mark on a copy sheet. The temperature of ink in the printhead is sensed, and a combination of power level and time duration of the electrical input signal for the heating element to result in a desired size of the mark of the copy sheet is selected, by entering the sensed temperature of the ink into a predetermined function relating the energy of the electrical input signal to the corresponding resulting size of the mark on the copy sheet.

Abstract: A thermal ink jet printer is disclosed which has a printhead that is maintained at a substantially constant operating temperature during printing. Printing on demand is accomplished by the ejection of ink droplets from the printhead nozzles in response to energy pulses selectively applied to heating elements located in ink channels upstream from the nozzles which pulses vaporize the ink to form temporary bubbles. To prevent printhead temperature fluctuations during printing, especially in translatable carriage printers, the heating elements not being used to eject droplets are selectively energized with energy pulses having insufficient magnitude to vaporize the ink.

Abstract: A continuous stream type ink jet printhead utilizing constant thermal pulses to perturbate the ink streams emitted through a plurality of nozzles to break up the ink streams into droplets at a fixed distance from the nozzles whereat the drops are individually charged by a charging electrode in accordance with digitized data signals. Each printhead has a manifold, a plurality of ink channels communicating at one end with the manifold and terminating at the other end with nozzles, and at least one resistor addressed by a predetermined frequency of current pulses for applying thermal pulses to the ink. In one embodiment, a resistor is positioned in each of the channels adjacent the nozzles and in another embodiment, a single resistor is located in the ink manifold. The resistors are pulsed at low power to generate a perturbation of ink properties such as density, viscosity, or surface tension without producing a phase change in the ink.

Abstract: An improved photoelectrophoretic imaging method is disclosed wherein a blocking layer is provided with a coating which interacts, in the dark, with the pigment particles of the imaging suspension so as to provide a uniformly charged imaging suspension upon exposure of the suspension to an electric field. The coating material occupies at least a substantially equal position in the Dark Charge Injection Series as any pigment in the imaging suspension. Subsequent or simultaneous electromagnetic radiation to which at least some of the particles are sensitive then results in the formation of optically positive and negative images.

Abstract: An improved photoelectrophoretic imaging method is disclosed wherein the imaging suspension is brought into contact under a first electrical field with a blocking layer having a coating which interacts, in the dark, with the pigment particles of the imaging suspension so as to provide a uniformly charged imaging suspension. The imaging suspension is then exposed to appropriate electromagnetic radiation while under a second electrical field. A second blocking layer, free of said coating is employed to produce positive and negative images.