Hewlett-packard Company

C S Chan

Gary E Hanson

James G Bearss

Terry M Nelson

Robert R Hay

Conrad L Wright

Alfred I Pan

Wesley L Meyer

Bruce Cowger

Kenneth E Trueba

Wayne E Foote

Thomas Camis

Kenneth Eugene Heath

John A Thompson

Gar P Kelly

Frank Ura

James G Bearrs

A system for projecting electrically conductive or semi-conductive toner directly on to print media using a direct electrostatic projection printing device that includes a projection control electrode positioned between a reference electrode and an orifice plate. A mechanism is provided for generating a first electric field between the reference electrode and the orifice plate to form a cloud of toner particles between the reference electrode and the orifice plate. A mechanism is also provided for intermittently generating a second electric field between the projection control electrode and the orifice plate to project toner particles through the orifice plate on to a sheet of paper.

Toner projection system

A print apparatus includes a photoconductor and a mechanical system for moving the photoconductor past a scan line exposure station. The print apparatus includes a signal generator for providing outputs indicative of the movement of the photoconductor. A first comparator produces a first position error signal that is derived from a difference between a reference signal and a position error signal output, such position error signal indicating that the position of the photoconductor differs from a predetermined print position that is determinable with respect to the reference signal. The print apparatus further includes a laser beam scanner and a beam detector for producing a scan position signal. A second comparator is responsive to the scan position signal and the position error signal from the first comparator to produce a beam deflection control signal that is applied to a beam deflector having a mirror attached to a piezoelectric bimorph crystal cantilever element. The beam deflector moves the laser beam in a direction which reduces the beam deflection control signal and position the laser scan at a position closer to a predetermined print position.

Laser printer with piezoelectric apparatus to reduce banding by

An electrostatic printing apparatus includes a rotating transfer drum having an outer transfer surface. A plurality of direct toner projection units are positioned adjacent the transfer surface of the rotating transfer drum to project toner patterns of different colors onto the transfer surface in response to modulated signals. After the patterns are applied to the drum, they are transferred to paper and fused. The drum is constructed of two components: a base layer or core which is conductive, and a surface layer which is chosen primarily for its surface properties. The surface layer is conductive enough to allow toner particles to dissipate their electrical charges before additional toner is applied by downstream toner projection units.

Direct toner projection printing using an intermediate transfer medium

An electrostatic imaging system includes a photoconductor which carries an image defined by a liquid toner. The liquid toner comprises a pigment binder system in a paraffinic solvent blend carrier liquid, the liquid carrier exhibiting a relatively high flash point temperature. The imaging system further includes a heating roll, and a film forming roll positioned between the photoconductor and the heating roll. The film forming roll includes at least first and second superposed layers, the first layer comprised of a material that is carrier liquid phillic and which exhibits a dimensional thickness which enables substantially all carrier liquid entrained therein to reach the liquid's flashpoint temperature when under influence of the heating roll. The second layer is carrier liquid phobic and exhibits a resiliency that enables the first layer to compliantly mate with the photoconductor surface. A further transfer roll comprises an outer, liquid carrier phobic layer and an inner compliant layer for enabling indirect transfer of an image from the photoconductor to a media sheet.

Liquid toner fusing/transfer system with a film-forming roller that is

A pixel assignment and error diffusion system and method for gray scale printing in one or more color planes in the fields of ink jet printing, electrophotographic printing, or the like. The direction of each error diffusion with respect to the location of a just-scanned or just-processed super pixel within a larger scanned area is controlled by the contemporaneously developing gray scale profile and gradient over a previously scanned area defined by a predetermined number of previously scanned super pixels. This developing gray scale profile and gradient of a scanned image is used to select a matching error diffusion set of diffusion points, each having a relative weight W and a location L, from a chosen look-up table stored in memory. The relative weight W is proportional to the gray level intensity of the developing profile and the location L is proportional to the slope of the gradient of a family of gray level profile or contour lines, wherein the gradient is generally perpendicular to these lines. The selected error diffusion set is in turn used to control the direction and weighted distribution of an error remainder value R into areas of a processed image adjacent each just-scanned or just-processed super pixel within a larger scanned area.

Method and system for printing in one or more color planes with improved

An ink delivery system for an inkjet printer includes a vented supply chamber for providing a reservoir of ink and an ink compartment which is connected to the supply chamber via a hydrophobic membrane which acts as a fluid diode for regulating the flow of ink from the supply chamber into the compartment.

Ink delivery system for printers

A system for delivering ink to print heads in thermal ink jet printers includes a liquid compartment with a gas space thereabove at sub-atmospheric pressure, a hydrophobic membrane mounted between the liquid compartment and the surrounding environment for allowing ambient gases to bubble into the liquid while preventing liquid from flowing in the opposite direction through the membrane, at least one chamber that provides a reservoir of ink with a gas space thereabove at sub-atmospheric pressure, and a manifold connecting the gas space in the liquid compartment with the gas space in the ink chamber. Thermal ink jet print heads are mounted in ink-flow communication with the ink chamber and are adapted for ejecting ink onto sheets to be printed. In operation, ink flows into the thermal ink jet print heads at a flow rate which is regulated by a generally constant back pressure. This novel pen body construction enables the hydrophobic membrane to be completely isolated from the ink in the multiple ink reservoirs of the pen, with the advantage that ingredients and additives within the ink do not degrade the surface properties of the hydrophobic membrane material.

Ink delivery system for ink jet printers

A method of gray scale printing of dots of one or more colors into pixels and in a controlled ordered sequence into a plurality of super pixels defined by a given number of said pixels, characterized in that: one or more levels of dot loading are used to achieve different values of gray level in a multiple-level gray table. This generic method is applicable to both ink jet and electrophotographic printing species of this invention. In one electrophotograpic printing species of this invention, there is disclosed a method of electrophotographic color printing which includes mixing a plurality of colors in a single plane and in dot-next-to-dot (DND) pixels within a plurality of super pixels to produce a color image, whereby the sum of the multi-color dots printed in any super pixel is limited to the number of subdivided individual pixels therein, thereby assuring dot-next-to-dot (DND) always printing of said colors in a single plane. The above method further includes varying the area of each printed color dot within each pixel of a super pixel in order to control the gray scale of a printed color image. Gray scale printing is achieved by controlling the selection of a gray table entry level number representative of one of several available entry level numbers corresponding to a plurality of different dot loadings for a corresponding plurality of differently printed super pixels.

Method and system for enhancing the quality of both color and black and

A method and system for continuously correcting for errors in color output of a color copier or printer and caused by events that occur between the input of a color image scanner and the output of a copier or printer driven thereby. This method and system includes, among other things, the continuous comparison of input test pattern data, TP.sub.in, from a small color gamut or 'patch' having only a selected few number of color pixels therein with the output test pattern data, TP.sub.out, from a color printer or copier to generate a color correction conversion factor, H. Then, H is used to continuously update an initial full scale look up table which was initially prepared from a full scale color gamut. The initial look up table has a color conversion factor, F.sub.old, and H is used to convert F.sub.old to F.sub.new where F.sub.new =H.multidot.F.sub.old. In this manner, H continuously corrects for undesirable changes in parameters used to generate the initial look up table, such as quality of print media, ink, dye loading, ink drop volume, pen types and the calibration of system devices.

Method and system for providing closed loop color control between a

A method and system for color and monochromatic printing wherein ordered dither and error diffusion processes are combined to provide high quality printed images with good spatial resolution, good gray scale transitions, good low frequency and high frequency responses and a high computational speed. Using this process, gray scale numbers representative of a scanned image are summed for each super pixel of the scanned image and divided by a chosen gray level normalizing factor. This division operation is done to obtain a normalized ordered dither quotient number of drops (dots) to be printed in super pixels and to further obtain an error remainder number of dots to be dispersed to surrounding super pixels. The normalized ordered dither quotient number of dots are printed in pre-assigned individual pixels within printed super pixels, and the error remainder number of drops are diffused to other pre-assigned surrounding or adjacent super pixels. In this manner, a combination of ordered dither and error diffusion signal processing and printing is achieved to simultaneously take advantage of some of the best characteristics of both types of signal processing printing. In color printing, the above operation is carried out in each of a plurality of separate color planes, and all of the quotient information is retained and printed in a predetermined priority sequence for each color plane.

Method and system for reproducing monochromatic and color images using

A hybrid type thermal ink jet (TIJ) pen and method of manufacture wherein a plurality of individual thin film ink jet printheads, each including an orifice plate, are selectively spaced on and secured to an insulating substrate having ink feed ports therein which supply ink to the printheads. Buss lines and integrated circuit driver-decoder packages may be mounted in a planar fashion with respect to the printheads and electrically interconnected to drive the printheads. Alternatively, the individual printheads may be mounted on a unitary insulating support and ink feed structure such as a ceramic substrate and interconnected to off-substrate TIJ driver circuitry by way of printed or silk-screened electrical leads. These leads may be laid down in a controlled pattern on the surface of the ceramic substrate and used to interconnect bonding pads on the TIJ printheads with the above off-substrate driver circuitry and power supplies. If desired, integrated circuit packages may be mounted in slots cut in the ceramic substrate in a planar arrangement with respect to the printheads.

Large expandable array thermal ink jet pen and method of manufacturing

An apparatus for rapidly coupling and decoupling a remote source of ink supply to a disposable ink jet pen filled with a porous ink storage material. This is accomplished without requiring an air-tight seal at the connection of ink into the pen, and is characterized by the use of a capillary tube which extends from the remote source of ink supply to the pen. The capillary tube has a needle mounted at one end thereof for easy penetration into and removal from the porous material within a storage compartment of the pen. The capillary action of the porous material acting on the needle is used draw ink by capillary action from the remote source of ink supply into the pen. This action allows the free liquid surface of the remote ink supply to be positioned below an ink ejection plane of the pen, thereby preventing ink from drooling from the pen during ink jet printing.

Ink supply apparatus for rapidly coupling and decoupling a remote ink

A method for reducing 'grainyness' or color contrast in color imaging systems and simultaneously reducing or eliminating paper cockleing of media printed by ink jet printing. The method involves determining the maximum allowable ink print density necessary to reduce or eliminate paper cockleing in the printed media and then providing tight control of the selection of gray scale ink drop count and associated dye loading in relation to this maximum allowable print density. Using this method, pixels are selected and printed in such a manner as to maximize the uniformity of ink distribution on the printed media. This method will work using either a variable drop size or a fixed drop size with variable dye loadings. It will also work with most error diffusion or dithering schemes presently used and available in the image processing arts.

A system for supplying ink to an ink jet pen wherein an off board ink supply is provided remote from the pen, and ink is fed from this supply to the pen by capillary action created during an ink jet printing operation. The pen includes a porous storage medium which is initially filled with ink at a slightly negative head. However, this negative head increases during ink depletion from the storage medium and provides the capillary forces necessary to pull ink into the storage medium from the off board ink supply. The driving energy for this action is provided by current drive to a thin film printhead of the pen, thus rendering the printhead multi-functional in purpose and simplifying the ink supply apparatus therefor. The use of an intermediate porous storage medium enables the ink supply system to accommodate large rates of changes in ink demand from the pen while still affording the user with a large ink capacity system in which disposable pens may be readily and easily replaced in a user-friendly operation.

Off board ink supply system and process for operating an ink jet printer

A plastic orifice plate for an ink jet printhead and manufacturing process therefor which includes electroforming a metal die having raised sections thereon of predefined center-to-center spacings, and using the die to punch out openings in a plastic substrate of a chosen thickness to form a plurality of closely spaced orifice openings in the substrate. The orifice plate can be of a chosen transparent material and secured to a printhead substrate where the dynamics of ink flow can be viewed through the orifice plate during printhead testing and evaluation.

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Boise, ID, United States of America

C S Chan