Abstract: In a printhead for electrostatic printers, the styli of the printhead are formed on a monolithic substrate, such as a printed circuit board. Each stylus has its own driver circuit incorporated into one or more integrated circuit die which are mounted directly on the monolithic substrate, and electrically connected to traces formed on the printed circuit board. The styli are the ends of the traces as formed on the edge of the substrate. The integrated circuit die are connected to the traces by wire bonding or TAB bonding. The printhead is implemented in monoscan, biscan, triscan, and various other configurations.

Abstract: Each of the plurality of styli contained in an electrostatic print head and used for placing an electrostatic charge on a dielectric coated medium has a rectangular cross section. The thickness of the cross section is selected such that the difference between the lowest voltage on the stylus at which the amount of electrical charge deposited on the dielectric medium for any increase in voltage on the stylus increases substantially in a linear fashion and the lowest voltage on the stylus at which an unwanted background image is formed on the medium is selected to have a value equal to or less than a selected number. In one embodiment this thickness is selected to minimize this difference. In another embodiment this thickness is selected to ensure that the electrostatic print head performs for some minimum lifetime.

Abstract: In a printhead for an electrostatic printer, the printhead styli are formed on a monolithic substrate, such as a printed circuit board material. Each stylus has its own driver circuit incorporated into one or more integrated circuit die which are mounted directly on the monolithic substrate, and electrically connected to traces formed on the printed circuit board. The styli are the ends of the traces as formed on the edge of the substrate. The integrated circuit die are connected to the traces by wire bonding or TAB bonding. The printhead is implemented in monoscan, biscan, triscan, and various other configurations. To fabricate the printhead, the printed circuit board material is ground to a precise thickness and conductive traces are photolithographically etched in copper foil laminated thereto. Using adhesives, the printhead is laminated together including supporting side plates, and in some embodiments multiple substrates, which are laminated together directed or by spacers therebetween.

Abstract: A sensor assembly is provided in which a balanced pair of sensors is provided by abutting two optical devices each having a light emitting diode of infrared emitting diode type (IRED) and a photosensitive transistor. By using only one IRED which is located between the photo-sensitive transistors, a substantially identical image of an object placed above the IRED is provided to simultaneously to each of the phototransistors. The sensors mounted on a printed circuit board are also aligned to windows on a surface of the sensor assembly automatically by providing projections, preferably cylindrical, on the inside walls of the sensory assembly and complementary recesses on the printed circuit board. Signals are transmitted to a multiplicity of printed circuit boards simultaneously by threading conductors through holes situated at predefined locations on each printed circuit board.

Abstract: A plurality of hues of color or shades of grey are obtained on a print medium using an electrostatic printer by varying either or both the voltage applied to each styli in the print head and the time of application of such voltage.

Abstract: A start of plot mark consists of three portions, a first, second and third portion each of equal area with the first and second portions being above a reference line and spaced from each other by the second portion which is below the reference line. The first and second portions are used to generate a reference signal for use in measuring the zero crossing of the output signal from the start of plot mark thereby to automatically compensate for uncertainties in the zero crossing such as those uncertainties produced by differences in intensities of the start of plot coloration versus the background coloration of the print medium, differences in reflectivity and illumination of the print medium, and imbalances between sensor output signals.

Abstract: A registration system is provided for maintaining accurate correspondence between an image on a moving substrate and the action of an operating element with respect to the substrate. A comparison optical device is mounted such that the timing marks pass in correspondence with the comparison optical device when the substrate is moving. A detector senses the intensity of radiation reflected from the substrate through the comparison optical device and generates a firing signal based on the reflected radiation intensity. The firing signal is provided to the operating element to activate it in correspondence to the passage of the timing marks.

Abstract: A system for activating an operating element with respect to a moving substrate comprises a tracking line formed on the substrate, the tracking line having an activation mark formed therein which reflects light of an intensity which is distinguishable from that reflected from the remainder of the tracking line. A photosensor is mounted in relation to the tracking line to sense the intensity of light reflected from the tracking line when the substrate is moving. The photosensor generates an output signal indicative of the passage of the activation mark with respect to the photosensor. The output signal is utilized to activate the operating element.

Abstract: An electrostatic printing apparatus is disclosed having an improved optical scanner. The optical scanner is capable of directing a beam of radiation about a circular target zone. The scanner includes hollow shafted rotor having focusing and deflecting elements, rigidly mounted therein. The scanner can be readily adjusted to eliminate any timing errors.

Abstract: An electrostatic printing apparatus is disclosed wherein a photoconductive material is irradiated to activate a stylus array. In accordance with the subject invention, the write time of the stylus array can be controlled thereby improving contrast ratio. This result is achieved by providing a second discrete photoconductive layer which is irradiated a fixed time after a first photoconductive layer. The second photoconductive layer is connected in a manner to shunt current from the stylus array thereby effecting the write time.