Abstract: A modulator circuit for use in driving a laser in an electrophotographic laser printer starts with a standard, inexpensive low-frequency pixel clock for timing the modulation of the laser to form an image, and effectively doubles the modulation frequency, thereby allowing spatial resolution to be doubled in the fast-scan direction. An original, low-frequency pixel clock is split, one of the split signals is delayed by a predetermined amount, and the original and delayed pixel clocks are applied to an exclusive OR gate. The modulator of the present invention functions without either a high-frequency original pixel clock or a phase-locked loop.

Abstract: An ink-jet printhead in which an orifice for the passage of ink therethrough toward a preselected location on the sheet is shared by two ejectors. Each ejector is capable of emitting ink of a preselected quantity through the orifice. The ejectors may be activated substantially simultaneously, to cause ink of a combined quantity to be emitted through the orifice.

Abstract: A system for converting RGB color signals to CMY or CMYK color signals, such as to operate a color printing apparatus, utilizes three separate electronic look-up tables. Each look-up table allows inputs of RGB signals, which are applied to a three-dimensional space. Each point in the space represents an output for one CMY color signal, and each look-up table is dedicated to one CMY color output. Each look-up table emphasizes one particular RGB color, by providing a higher resolution of inputs along the axis for that color.

Abstract: A printed wiring board includes features which allow the board to be held firmly in place by a vacuum mounting device so that semiconductor chips can be placed thereon, and wire bonds established between the semiconductor chips and the circuitry on the board. The side of the board opposite the side having the semiconductor chips defines a ridge which encloses a portion of the surface area thereof. The ridge forms a gasket around a vacuum slot on the vacuum mounting device. The ridge also provides a firm surface for wirebonds to be ultrasonically welded to landings on the board.

Abstract: A raster output scanner for use in an electrophotographic printer uses two light sources to create two scan lines on a photoreceptor simultaneously. The two light sources are operated in an alternating fashion, and the intensity of the light sources is monitored by a single sensor. The sensor is associated with a reflex-based exposure control system, which operates to shut off a particular light source when the exposure created by the light source reaches a threshold level.

Abstract: A system enables high-resolution videoconferencing images to be transmitted, without extreme demands on bandwidth. A mosaicing camera sequentially samples a series of small portions of a general scene, and a composite image of the entire general scene is transmitted. Simultaneously, an individual small area of the general scene where high time resolution is desirable is sampled at a high time resolution by a dedicated camera. The high-time-resolution images are then patched into the composite image.

Abstract: Semiconductor chips, such as photosensor arrays for a full-page-width scanner or printhead chips for a full-page-width ink-jet printer, are mounted on a substrate to maintain reasonably consistent spacing among adjacent chips. To remove a defective chip from the array, the substrate is urged evenly against a work surface defining a convex bow. Alternately, back-cuts are provided along abutting edges of the chips, and the silicon around these back-cuts can be sawed away to space defective chips from neighboring good chips. By increasing the spacing of a defective chip from neighboring chips, the defective chip can be removed while minimizing the risk of damage to neighboring chips. Also, batches of chips can be originally manfactured on a single wafer as either "regular" chips or "replacement" chips, with the replacement chips being slightly shorter in a critical dimension.

Abstract: A customer-replaceable module having a fusing subsystem therein for a electrophotographic printer or copier includes three separate devices for detecting potentially dangerous temperature conditions within the module. A first thermal cutoff spaced from the fuser roll can detect high temperatures caused by incorrect software operation and hardware failures. A second thermal cutoff contacting the fuser roll outside of the paper path can detect failures associated with software malfunctions and paper shielding the first thermal cutoff. A thermistor contacting the fuser roll in the paper path can interface with the control software of the printer or copier itself. The thermal cutoffs function entirely independently of the control software of the printer or copier. The module may further include an electronically-readable memory for recording failure conditions.

Abstract: An ejector for a thermal ink-jet printhead includes a heating element defined on a main surface of a silicon heater chip. A cavity is disposed within the heater chip opposite the side of the heating element exposed to liquid ink. In one embodiment, the heating element is disposed on a narrow pillar which is surrounded by two elongated trenches. In another embodiment, the heating element is suspended over a cavity by narrow supports. In each case, the cavity reduces the thermal mass of the structure supporting the heating element and acts as an insulator to prevent excess heat from being dissipated into the body of the heater chip.

Abstract: A thermal ink-jet ejector having a fluid flow channel extending between an ink inlet and a nozzle for the ejection of liquid ink therefrom, includes a rear channel diffuser disposed between the heating element and the inlet, and/or a front channel diffuser disposed between the heating element and the nozzle. Each diffuser includes an arrangement of tapers which decrease the flow impedance of liquid ink flowing toward the nozzle, and increase the flow impedance of liquid ink flowing toward the inlet. The arrangement increases the kinetic energy of droplets being ejected, and also increases the speed of re-fill of the channel with liquid ink following ejection.

Abstract: An architecture of a fuser subsystem in an electrophotographic printer or copier includes a web which cleans the fuser roll. The web is driven by a mechanism which enables a constant velocity of the web relative to the fuser roll surface without the need of separate motor or controller. The design can further compensate for changes in frictional coefficient between the fuser roll and the web, such as is caused by large deposits of toner collected on the cleaning web.

Abstract: A technique for calibrating the hardware and software of a digital printing apparatus relies on making seven component test patches which completely characterize the printing system, and then measuring the actual reflectance of these seven test patches. The measured reflectances are then converted, by the Yule-Nielsen equation, to values representative of the ink area coverage characteristic of each component test patch, because ink area coverage is the parameter that can be directly controlled by the digital printer. This conversion step takes into account the non-linear relationship between the reflectance of a halftone area and the amount of ink area coverage on the halftone area.

Abstract: A method and system segments an original image to be scanned and reproduced by a digital copier utilizing a scannable window location carrier. To realize the segmentation, an original image is inserted between a transparent portion and a highly reflective portion of the scannable window location carrier. The scannable window location carrier has a standard sheet size. An edge of the transparent portion and an edge of the highly reflective portion are permanently bonded together, and the transparent portion and the highly reflective portion are of identical lengthwise and widthwise dimensions. The transparent portion is marked so as to create a boundary outlining an area of the original image that is to be segmented from another area of the original image. The original image is removed from between the transparent portion and highly reflective portion of the scannable window location carrier, and the scannable window location carrier is scanned.

Abstract: In a development unit for electrostatographic printing, where toner particles are conveyed by a rotating roll to a charge-retentive surface, a groove is defined in the interior surface of the housing which retains the toner particles, the groove extending along a portion of the circumference of the roll. The groove facilitates redistribution of toner particles which accumulate at the bottom of the housing near an end of the roll.

Abstract: In a xerographic development unit, particularly a unit for applying single-component magnetic toner such as used in MICR printing, the end of a donor roll which applies toner to the surface of a charge receptor is provided with a magnetic seal. The magnetic seal extends around at least a portion of the circumference of the roll, and defines a set of alternating magnetic poles arranged in bands which alternate along the length of the roll. The magnetic seal forms a uniform gap relative to the surface of the roll, the gap being sufficiently large to allow a turnover of toner particles therethrough. The design minimizes mechanical stresses on the toner, which in turn avoids the generation of frictional heat in the toner. A member defining magnetic poles can also be used as a shim for mounting a charge/metering blade within the development unit.

Abstract: An ink-jet printhead fabrication technique enables capillary channels for liquid ink to be formed with square or rectangular cross-sections. A sacrificial layer is placed over the main surface of a silicon chip, the sacrificial layer being patterned in the form of the void formed by the desired ink channels. A permanent layer, comprising permanent material, is applied over the sacrificial layer, and, after polishing the two layers to form a uniform surface, the sacrificial layer is removed. Preferred materials for the sacrificial layer include polyimide while preferred materials for the permanent layer include polyarylene ether, although a variety of material combinations are possible.

Abstract: An expert system, such as could be used for service of a complicated physical device such as a printer or copier, exploits a knowledge base which is written in a markup language format such as SGML. The knowledge base comprises text which, if desired, can be printed out on paper to yield a traditional service manual. In addition to the typical formatting markup language tags surrounding the text of the knowledge base, hierarchical tags are provided in the electronic version of the knowledge base, to define a set of decision trees which can be accessed and navigated by an expert system. A diagnostic advisor can access specific elements of the knowledge base as needed to synthesize optimized diagnosis and repair procedures depending on an entry given by a tech rep servicing a machine. This arrangement thus supports both a printed service manual and a viewer that provides expert diagnostic advice.

Abstract: In a scheduling system which optimizes a sequence of operations for carrying out, for example, digital printing of simplex and duplex documents, a "schedule tree" is created and updated in real time. The schedule tree is a running list of all possible schedules or sequences of operations within a future time frame, given a desired output of documents. Various techniques are used to manage the size of the tree and select schedules from the schedule tree to be proposed to the printing apparatus over time.

Abstract: A control system for the laser diode of a raster output scanner, such as used in a laser printer, uses reflex exposure control and a high-speed drive circuit. With the creation of each pixel on the photoreceptor, a sensor receiving some of the light flux from the diode accumulates charge on a capacitor, and when the charge on the capacitor exceeds a predetermined amount, a reflex circuit acts to shut the laser diode off. The laser diode is modulated via a high-speed trigger circuit wherein the diode is maintained just below its lasing voltage.

Abstract: A monitoring system for replaceable units, such as toner cartridges in an electrophotographic printer, includes on the unit an electronic count memory and an electronic flag memory. The count memory maintains a one-by-one count of prints made with the cartridge. The flag memory includes a series of bits which are alterable from a first state to a second state but not alterable from the second state to the first state. The bits in the flag memory are altered at predetermined intervals as prints are made with the cartridge. The flag memory is used as a check to override unauthorized manipulation of the count memory.