Abstract: A digital halftone pattern geometry adapted not to the characteristics of variable dot size printing presses but to the operating characteristics of the printer itself achieves a high degree of image quality. The techniques for creating the halftone pattern geometry include linear spot growth to provide uniform darkening and the use of a super-cell structure to maximize the number of tint or gray scale levels. A preferred super-cell structure is of hexagonal dispersed-dot form to reduce low frequency artifacts by spreading them over a greater number of frequencies. Hexagonal centered super-cells also distribute row and column artifacts along three axes of symmetry instead of two. The super-cell structure gives sharp edges and a greater amount of edge area available to manipulate when the super-cells are tessellated to form an image. This halftone cell arrangement is especially suited to thermal transfer printers, which print linear rows and form good rectangular shapes.

Abstract: A conductive refractory compound coating for electrodes is sputter resistant, very resistant to oxidation, and easy to apply by way of electrophoresis or screen printing. This structure is further enhanced by the presence of surface particles of electrically nonconductive ceramic material. When the cathode electrode is energized, electrically nonconductive material is penetrated by the electric field, which attracts secondary electrons out of the cathode electrode, thereby increasing the cathode's efficiency as an emitter of secondary electrons. More specifically, cathode electrodes are used in a plasma addressing structure. The coating is formed by approximately 5 nm particles, each comprised of a fused matrix of conductive and nonconductive particles co-deposited with frit particles by either electrophoresis or "silk" screening. The coating is subsequently baked to fuse the frit and bond the electrophoretically deposited particles to the electrodes.

Abstract: A method and an apparatus reduce cross talk effects in electro-optical addressing structures. In a preferred embodiment, a flat panel liquid crystal display system (10) includes a layer (28) of frequency-sensitive liquid crystal material having a dielectric anisotropy that approaches zero for signal frequencies greater than a characteristic threshold frequency f.sub.th. The frequency-sensitive liquid crystal material is nonresponsive to components of signals with frequencies greater than the threshold frequency f.sub.th. A data driver (32) delivers inverted data signals (62) and conventional, noninverted data signals (64) to each of the multiple display elements (16) during successive first and second time intervals, respectively. As a result, the data driver generates cross talk having frequency components greater than the characteristic threshold frequency f.sub.th of the liquid crystal material.

Abstract: A halftoning method characterized by two nonaligned halftone screens, one for black and the other for the subtractive primary colors cyan, magenta, and yellow, produces multi-color images on a color laser printer. The black screen is the inverse of, i.e., in reverse fill order to, the subtractive primary colors screen. The halftone pattern is a vertical line screen. In a preferred embodiment, the cells are grouped on hexagonal centers and aligned along X and Y coordinate axes. The dots are grouped in the linear direction of print medium motion. The grouping of dots reduces the effect of halftone screen misregistration, and the cell alignment in X and Y results in fewer high frequency artifacts. Inverting the black screen increases the number of possible chromatic mixed colors that include black, increases color uniformity and reduces the frequency of white "holes" in the printed images.

Abstract: A refractory compound coating (188) for electrodes is sputter resistant, has a low work function so that it is a good emitter of secondary electrons, is very resistant to oxidation, and is easy to apply by way of electrophoresis. More specifically, cathode electrodes (162) are used in a plasma addressing structure (10). The coating is preferably formed by electrophoretic deposition of particles (184) of at least one refractory compound along with a frit. The coating is subsequently baked to fuse the frit and bond the electrophoretically deposited particles to the electrodes.

Abstract: A switchable color filter (11) includes three polarizing filters (12, 14, and 16) and two zero to substantially half-wave optical retarders (36 and 38) and is incorporated in a field sequential display system (10) to provide output states of light of three different colors to form an image in full color. Each one of four preferred embodiments (11, 11a, 11b, and 11c) of the switchable color filter provides the output states of three colors. The third and fourth preferred embodiments (11b and 11c) provide a fourth additional output state of, respectively, white light and light of a color which is a combination of two of the other output state colors. The optical retarders comprise nematic liquid crystal cells (100) having fast relaxation times to operate the display system at video rates.

Abstract: An addressing structure (10, 10') using an ionizable gaseous medium has plural nonintersecting channels (20, 20') extending in a first direction and filled with an ionizable gaseous medium. Each channel contains a reference electrode (30, 30') and a row electrode (62, 62'). An amplifier (100) provides a kicker pulse to one or both of the first and second electrodes in a channel at a time coincident with the application of a second electrical signal to the second electrode. The kicker pulse and the second electrical signal cooperate to promote ionization of the gaseous medium within a predetermined discharge initiation delay time tolerance. The ionization captures across a liquid crystal material (44) data signals placed on column electrodes (18); the data signals place display elements (16) associated with the electro-optic material in predetermined data storage or display element states.

Abstract: A photocurable polymer precursor added to a liquid crystal material polymerizes to form a mixture that significantly lowers the threshold and saturation voltages of a standard twisted nematic cell. The performance characteristics of the resulting display device resembles those of a device with a very high pretilt, thereby providing an economical method of fabricating liquid crystal cells of a type that require a high pretilt alignment. The presence of the polymer substantially reduces adverse ion-related effects such as optical droop and charge retention in the liquid crystal display device.

Abstract: A digital halftone pattern geometry adapted not to the characteristics of variable dot size printing presses but to the operating characteristics of the printer itself achieves a high degree of image quality. Techniques for creating the halftone pattern geometry include linear spot growth to provide uniform darkening and the use of a super-cell structure to maximize the number of tint or gray scale levels. A preferred super-cell structure is of hexagonal dispersed-dot form to reduce low frequency artifacts by spreading them over a greater number of frequencies. An increase in addressability to enhance printer resolution in the direction of the path of print medium travel with no change in dot size will cause placement of overlapping dots when a darkening of consecutive pixels in the direction of print medium travel is called for in the halftone pattern.

Abstract: A method and an apparatus (10) for cleaning an ink jet print head (12) draws contaminates from orifices (20) in the print head onto an orifice plate (14) and then wipes the orifice plate. The maintenance apparatus includes a purge cap (24) that has a recessed region (40) with an open end (36). The top side margins (42) of the open end define a periphery (44) around which a seal (60) is positioned. A positioning system (30) urges the orifice plate against the seal. A heating system (128) and a vacuum system (74) cooperate to create a differential pressure across the orifices to draw contaminates carried by liquid ink out of them and onto the orifice plate. A resilient wiper assembly (26) including a spring-mounted wiper blade (78) is positioned in and nominally extends outwardly of the recessed region of the purge cap. The positioning system moves the purge cap downwardly against the orifice plate so that the wiper blade engages and wipes the contamination from the orifice plate.

Abstract: A color liquid crystal display (LCD) includes many ones of a color cell triad (150) of liquid crystal cells (80R, 80G, 80B) and a negative birefringence compensator plate (110). The color cell triads are positioned between a pair of linear polarizers (112, 114), and each color cell triad is in optical association with colored filters (152R, 152G, 152B). Each of the liquid crystal cells has a symmetrical director field (82, 82') that produces a symmetrical but nonuniform color viewing circle curve (100) from the liquid crystal cell. The negative birefringence plate restores the color viewing angle uniformity. When graphed on a polar plot, the measured light transmission percentage curves (120, 122, 124) characterizing the LCD are substantially concentric circles surrounding the optical axis (18) for all azimuthal angles (28) and viewing angles (24) up to 30 degrees. Thus, the color LCD provides a multi-color display having colors that are perceptibly uniform over a wide range of azimuthal and viewing angles.

Abstract: An addressing structure uses an ionizable gaseous mixture having a decreased decay time to address data storage elements (16) defined by the overlapping areas of multiple column electrodes (18) on a first substrate (48) and multiple channels (20) on a second substrate (54). Each of the channels contains the ionizable gaseous mixture and includes a reference potential electrode that receives a data signal and a row electrode that receives a data strobe signal. The ionizable gaseous mixture contains an ionizable gaseous medium and ionized particles that are collisionally matched with the ionizable gaseous medium to produce an decreased decay time of the ionizable gaseous mixture. The decreased decay time of the ionizable gaseous mixture provides an addressing structure having high-speed addressing capabilities.

Abstract: A gray scale LCD cell device (116) combines a liquid crystal cell (80) having a symmetrical director field (82, 82') with a negative birefringence compensator plate (110) and interposes them between a pair of linear polarizers (112, 114). The symmetrical director field produces a symmetrical but nonuniform gray scale or color viewing circle curve (100) from the liquid crystal cell. The negative birefringence plate restores the gray scale or color viewing angle uniformity. When graphed on a polar plot, the measured light transmission percentage curves (120, 122, 124) characterizing the LCD are substantially concentric circles surrounding the optical axis (18) for all azimuthal angles (28) and viewing angles (24) up to 30 degrees. Adding colored filters (152) to a color cell triad (150) provides a basis for a multi-color display having uniformly perceived colors over a wide range of azimuthal and viewing angles.

Abstract: A switchable color filter (11) includes three polarizing filters (12, 14, and 16) and two zero to substantially half-wave optical retarders (36 and 38) and is incorporated in a field sequential display system (10) to provide output states of light of three different colors to form an image in full color. Each one of four preferred embodiments (11, 11a, 11b, and 11c) of the switchable color filter provides the output states of three colors. The third and fourth preferred embodiments (11b and 11c) provide a fourth additional output state of, respectively, white light and light of a color which is a combination of two of the other output state colors. The optical retarders comprise nematic liquid crystal cells (100) having fast relaxation times to operate the display system at video rates.

Abstract: A plasma addressing structure functioning as a display panel (52) includes an ionizable gas captured within a network (110) of intersecting channels formed by multiple spaced-apart islands (60) arranged in substantially parallel rows (62) projecting from the major surface (104) of an underlying substrate (64). The network of channels includes elongated channels (112) that are positioned between adjacent rows of islands, and spur channels (114) that extend between individual islands in each row and couple adjacent elongated channels. The gas in the network of channels is selectively ionized to address display elements (54), which are aligned with the islands positioned along each of the island rows. Each island has a top surface or plateau (128) that is spaced-apart from and substantially parallel to the major surface from which the island projects.

Abstract: Addressing apparatus that electronically address data sites of a digital array include electrodes (36, 38) manufactured with consistent electrical contact quality on the surfaces of projections (30) from a substrate (14). This is accomplished by providing such electrodes with portions that are offset to follow regions of more equal slope on the projections. The offset electrodes are of more consistent structural and electrical contact quality and thereby facilitate an increase in the yield of the manufacturing process.

Abstract: An improved electrode structure (42', 42") for an addressing structure using an ionizable gaseous medium has a plurality of plasma discharge channels (20') and a reference electrode (30', 30") and a row electrode (62') extending along each channel. The channels open into a plenum (118) for exhausting gases from the channels and introducing into the channels an ionizable gaseous medium at a predetermined pressure. The reference electrodes and the row electrodes enter from opposite ends of the channels, and the reference electrodes cross below the plenum. The row electrodes have an end (110) spaced from the ends (102) of the channels. The end of the row electrodes is separated from the end of the channels by a first distance (D) adequate to prevent undesirable plasma discharge while the electrode structure is operating. In a first embodiment (42') the reference electrodes have an end (112) spaced from a first perimeter seal (106).

Abstract: An apparatus for addressing data storage elements (16) uses an ionizable gas excited by an AC energy source to store an analog datum in and read an analog datum out of each of the storage elements. The storage elements are defined by the overlapping areas of multiple column electrodes (18) extending in a common direction on a first substrate (48) and multiple channels (20) extending in a common direction on a second substrate (54). A layer of dielectric material (46) separates the first and the second substrates, which are positioned face-to-face and spaced-apart with the direction of the channels transverse to that of the column electrodes. Each of the channels is filled with an ionizable gas and includes two row electrodes electrically isolated from each other. At least one of the row electrodes is isolated from the gas by a dielectric coating (65) to prevent nonuniform current flow in certain regions along the length of a channel.

Abstract: A light shutter system (10) incorporates a liquid crystal cell (12) operating as a variable optical retarder to selectively produce opaque and transmissive optical states corresponding to the respective first and second amounts of optical retardation of the variable optical retarder. The cell switches between a residual amount of retardation and an increased amount that equals the sum of half-wave retardation and the amount of residual retardation to provide a shutter system whose system retardation switches between zero retardation and half-wave retardation and thereby produces opaque and transmissive states with an optimal contrast ratio. The cell is positioned between a linear polarizing filter (14) and an elliptical analyzer (16), the latter including a linear polarizing filter (20) and an optical retarder (18) of fixed value.

Abstract: The present invention is a method and an electrical circuit (28 and 50) for effectively eliminating the effects of time jitter caused by metastable states by rejecting measurements made under timing conditions that could lead to the development of metastable states. In a preferred embodiment, the circuit of the invention effectively eliminates time jitter caused by metastable states in digital oscilloscope circuitry by determining in advance the timing conditions that can lead to such jitter and detecting whenever the transitions of trigger and trigger hold-off signals meet such timing conditions. The circuit then generates a "possible metastable" signal that can be used by the oscilloscope circuitry, or by the controlling software, to reject any measurement made under those timing conditions.