Abstract: Nonoptical properties of inks can be brought to bear in locating ink that is invisible to an automatic sensor. Physical characteristics of inks as liquids can be exploited to reveal their locations with surprising precision. The system includes an optical sensor. Using ink that is visible to the sensor, a preferably fractional fill pattern is printed on a region of a printing medium. Using ink that is invisible to the sensor, calibration indicia or other patterns are printed on particular portions of the same region. Bleed (running together of the liquids of the two inks) tends to convert the fractional fill pattern into a solid fill, within the particular portions that were also printed with the "invisible" ink. Resulting optoelectronic signals provide amply high contrast between (1) fractional fill in the particular portions where the "invisible" ink is applied and (2) the original fractional fill elsewhere.

Abstract: A multipass pseudo random masking system includes N number of sequenced pseudo random number generators each generating X number of randomly arranged individual pixel masking values to randomize the masking order of Z number of pixels in a given swath of image data to be printed by an n-pass print mode printer. A sequencer responsive to a print command initiates at least one n-pass printing sequence by the printer and includes an initializer that produces a seed value that is loaded into the individual N number of generators to initialize their sequencing at the same masking value so they produce the same repetitive sequence of X number of individual pixel masking values during each given swath of the printing sequence.

Abstract: A device for printing comprising a stationary inkjet-style pen, two stationary motors and a paper holder movable on two axes, a slew axis and an advance axis, wherein the paper is moved into the proper position for each step in the printing process by the paper holder and the two motors.

Abstract: The invention is a system for scanning a document. A light source illuminates the document; an imager receives light from the document and directs it toward a detector array which produces a corresponding array of electrical signals. The imager has several optical properties that are useful either individually or in combination. The imager is telecentric and thereby ensures that image size and magnification are insensitive to object displacement along the optical axis and image brightness is uniform independent of object off-axis distance. An aspheric element within the imager balances focus variation within the depth of field with spherical aberration and thereby provides nearly uniform image resolution. A diffraction pattern, carried by the imager, corrects for spectral dispersion which occurs when light passes from air into a refractive material. An imager with a reflecting surface provides a system that is subject to little or no chromatic aberration.

Abstract: One form of the printer inks multiple tonal levels, as for continuous-tone images. A generally randomized printmask controls the printer. What is randomized is, for each pixel respectively, an indicator of whether to print or not. Each indicator is, preferably, a discriminator number for comparison with desired-image data--specifically with a desired tonal level, at each pixel, for the desired color image--to make each printing decision. Preferably the printer is thereby deciding whether to deposit a certain number of drops per pixel; it compares the discriminator with a particular number of desired drops, for the desired image. The discriminator at each pixel is in general different for multiple passes and these discriminators for the passes form a sequence. The sequence, for each pixel., is preferably selected at random from a multiplicity of sequences. Preferably the sequence for each pixel is preselected at random; and the selected sequences for all pixels are prestored in nonvolatile memory.

Abstract: A high speed full color inkjet printer switches automatically to a best print mode relative to minimum operating ambient temperature and a user selected printing media selected from a group of different types of medium.

Abstract: A scanner includes a photodetector, and encoder and an exposure control. For each line of pixels detected by the photodetector, the exposure control starts the exposure time and then stops the exposure time after a specified amount of relative motion has been detected. Thus, variations in the amount of relative motion cause inversely proportional variations in the exposure time to ensure that exposure time for each line of pixels corresponds to the same displacement. The exposure control can compensate for unavoidable position and velocity errors encountered in a dc motor drive and thereby allows a dc motor drive to be used in low cost commercial scanning products.

Abstract: At least two different printmasks are used for different printing devices--such as inkjet pens--that operate concurrently, or different printing steps that proceed concurrently, to produce respective image swaths in a single, pixel-based printing machine. In one form of the invention, the different printing devices produce different respective pixel-row pitches (related to resolution) on a printing medium, and the different printmasks help to minimize adverse patterning effects that result from interaction of the different pitches with dot-placement errors. The different pitches on the print medium may be provided through different pitches of marking devices (for example, the number of inkjet nozzles per unit distance along a pen) or in other ways.

Abstract: A document scanner having a scanner carriage with an integrally formed light monitor window and tab provides a positive, reliable feedback path for adjusting digital image gain controls to provide a uniform digital image during and after an initial lamp warm up period of time.

Abstract: An automatic document feeder is constructed of three chassis. A main chassis carries the active components, such as paper pick and drive mechanisms for sequentially picking and delivering said sheets to and from a flat bed scanner, motors, and transmissions for driving said paper pick and drive mechanisms, a document backing assembly, and electronic controller equipment. Moreover, the main chassis provides a document input tray. A lower chassis forms a low height form factor output tray, using paper stiffness caused by predetermined bending to register the document sheets without having to support the full length thereof. When assembled with an upper chassis, the three chassis provide the entire paper path. The lower chassis carries an attachment hinge mechanism for mounting the automatic document feeder appropriately to a flat bed scanner apparatus. The paper loading and unloading drive mechanism provides a balance normal force from a plurality of paper drive rollers.

Abstract: Different print quality modes in a printer such as a color inkjet printer invoke different print rendering options for a particular object to be printed. In an exemplary embodiment, a printer control automatically invokes an error diffusion haltoning technique for photo images whenever high quality mode is designated, and automatically invokes a dither haltoning technique for photo images whenever a normal or fast print mode is designated.

Abstract: Two methods of calibrating Fax machines are disclosed. The first method utilizes a pre-printed calibration chart and a computer connected to the Fax machine to be calibrated. The calibration chart is fed into the Fax machine which sends the resultant data to the computer. This data is analyzed by the computer to determine when the Fax machine started to scan the calibration chart. If the scan process did not occur at an optimum point, the computer sends a correction value back to the Fax machine to cause the Fax machine to begin scanning subsequent documents at an optimum point. In the second method, a calibration chart is printed by the Fax machine and then fed back into the machine. A copy of the scanned calibration chart is made to determine at what point the Fax machine began scanning the chart. If the Fax machine did not begin scanning at an optimum point, a user reads the copy and manually enters a corrective offset in to the Fax machine such that subsequent documents are scanned properly.

Abstract: An automatic document feeder includes a low profile, small footprint document output tray having an overall length of about one-half a document length and a shallow curvature with a centrally disposed medium depressor at the central region of the curve that forces a medium sheet to stiffen and to take the curved shape of the output tray.

Abstract: A full color copier having an inkjet printer includes a controller and algorithm for switching automatically intra page between one of two independent high speed carriage velocities and between one of two independent pen firing frequencies for maximize throughput relative to low ink density and high ink density graphic images to improve print quality images having densely inked areas by substantially reducing ink pen starvation, droplet trajectory errors, and fuzzy text edges.

Abstract: An automatic document feeder having a quick release hinge assembly for attachment to a computer input device having a medium receiving surface and an associated aligned flat bed bezel with at least one receiving sleeves includes a plurality of interconnectable modular assemblies where one of the assemblies functions as a hinge mount and includes a set of protrusions complementary in shape to a corresponding set of stops tilts on an attachment hinge secured removably to the hinge mount. The attachment hinge and hinge mount cooperate to permit the automatic document feeder to be swiveling mounted to the computer input device in a precisely aligned manner to facilitate the moving of documents in seriatim from an input tray to an output tray of the automatic document feeder via the medium receiving surface of the computer input device.

Abstract: An automatic document feeder mounted removably to a computer input device having a medium receiving and supporting surface includes a plurality of interconnectable modular assemblies for defining a medium path that extends from a medium input tray to a medium output tray via the medium receiving and supporting surface of the computer input device. One of the modular assemblies is a main chassis assembly includes an integrally formed main chassis shell having a substantially planar base. The input tray extends upwardly from the base and has a document receiving surface with a concave shape in both the vertical and horizontal planes to help facilitate proper sheet stiffening and alignment for sheet loading purposes onto the receiving and supporting surface of the computer input device. A paper pick and transport mechanism is housed in the main chassis and protrudes through a set of apertures in the output tray.

Abstract: A technique for document edge detection in an optical scanning system. The document is placed against an over-sized neutral background. A linear optical sensor array is used to provide successive lines of pixel data representing the luminance of detected pixel areas. Commencing from one end of the line of pixel data, for successive current pixels being tested, a group of n adjacent pixel values is correlated with a successive group of n adjacent pixel values to provide a correlation value for the current pixel. One of the groups is assumed to contain only background pixels, and their luminance is approximated to be equal to the average luminance over the entire background. If the correlation value exceeds a threshold constant, the current pixel is chosen to be an edge in this line of pixels. Data from several lines is processed to find corresponding edges for each line, and the line edges are subjected to a least squares fit to calculate the location of the document edge.

Abstract: A method and apparatus for enhancing the quality of images printed by dot printers or dot displays are disclosed. Image irregularities caused by quantization are smoothed by using a set of rules to transform an initial pattern into an enhanced pattern for printing. The initial pattern may consist of a matrix of bits representing an image having X dots per inch along an intended direction of printing. An intermediate pattern is formed by replicating columns of bits from the initial pattern. Image enhancement rules are applied to the intermediate pattern to invert one or more bits in the intermediate pattern to create an enhanced pattern. The enhanced pattern is printed at n*X dots per inch along the direction of printing where n.gtoreq.1.