Abstract: A method for achieving multiple exposure levels for IOI (IMAGE-ON-IMAGE) xerography when imaging a second color through a first toner layer previously developed on the photoreceptive member. In the example illustrated the data from the previous image paths (magenta and yellow) is analyzed. If the signal indicates that a magenta or yellow bit is present, the cyan output bit information passes to the ROS unchanged, or at full intensity. If however, the magenta and yellow are not present, a modified pattern providing an appropriate reduced exposure signal is sent to the ROS. The process of laser attenuation is blended with halftoning logic to avoid image degradation due to the attenuation.

Abstract: The present invention is a super-scalar method and apparatus for the generation of halftone dot patterns in an image processing system. The super-scalar design employs at least one block of memory for the storage of at least one predetermined halftone dot pattern across a plurality of unique locations therein, and a sequencer for producing an index into said memory as a function of the position of the pixel along a scan line and the halftone dot characteristics. Also included is addressing circuitry for memory access control, to combine the index produced by said sequencer and a pixel value for the pixel to produce a memory address, the memory address being thereby employed to access one of said locations in memory and to cause said memory to output a signal representative of a portion of the halftone dot pattern stored at the unique addressed location.

Abstract: An ionographic printer directs a stream of ions from a source to a charge receptor to create an electrostatic latent image thereon. The ion stream passes through a relatively large aperture having associated therewith a pinch electrode for narrowing the ion stream to a preselected width, and displacing electrodes for positioning the narrowed ion stream within the aperture. Varying the biases of the displacing electrodes causes the ion stream to scan across the aperture to deposit multiple spots of charged areas at desired locations on the receptor. The electrodes can be designed to compensate for spot placement skew and anomalies in the cross-sectional shape of the displaced ion stream.

Abstract: Mounted at every other intersection of the deflection planes of the ink droplets issued by a multi-nozzle printhead of a pagewidth continuous stream ink printer are two-dimensional differential optical sensors. These sensors are located near the printing plane and gutters of the printer and comprise first and second input optical fibers, each having one end coupled to a common light source and the other free ends directing light towards aligned confronting free ends of respective associated pairs of output optical fibers. One of the input fibers and its associated pair of output fibers are inclined with respect to the other, though both input fibers and their associated pair of output fibers are either coplanar or contiguous with the same plane.

Abstract: A ink jet printer having a reciprocating printhead with a single jet to print full pages of information on a recording medium by printing contiguous swaths of information. The recording medium is stepped a distance of one swath height after each swath is printed. A height control sensor is located on one side of the recording medium to receive periodically one or more sweeps of test droplets. The height control sensor has upper and lower pairs of photodetectors to detect droplets passing thereby and to produce differential sensing signals which identify the droplet having a trajectory closest to the desired trajectory. By determining the number of droplets between the identified droplets, the interdroplet spacing and drift of the droplet trajectories is monitored. In response to the height control sensor signals, the printer controller with associated circuitry adjusts the operating parameters of the printer to correct and to maintain the desired droplet trajectories and interdroplet spacings.

Abstract: An improved continuous stream ink jet printer is disclosed that conducts pagewidth printing via an array of fixed nozzles which direct droplets towards a moving recording medium. Each nozzle is assigned a segment of a printable line that extends across the entire width of the recording medium. The droplets from each nozzle are charged with printing information and fanned along its segment to specific pixels locations or to a gutter for recirculation. Distance sensing sensors are located below the droplet trajectories, parallel to the recording medium surface and perpendicular to the direction of movement of the recording medium. The distance sensing sensors periodically produce signals representative of the actual throw distance of the droplets and compare the signals indicative of the actual throw distance to a signal representative of the distance from the nozzles to a predetermined printing plane.

Abstract: An improved ink jet recording interlace strategy. Sequentially generated ink droplets directed to a recording medium are first charged and deflected by a uniform electric field. The charge sequence on the droplets is such that the droplets are separated by the electric field as they travel toward the medium thereby reducing electrostatic and aerodynamic interactions between droplets. The separation of droplets conforms to an interlace scheme wherein droplets directed to closely adjacent recording medium locations are separated by a number of droplets whose placement of said medium conforms to a multi-level interlace such that the scan direction of the number of droplets is disrupted at least once. In this way, sequentially generated droplets are directed to non-sequentially pixel locations in non-sequential interlace portions of the total number of adjacent pixel locations assigned to a particular nozzle.

Abstract: In a digital printer, method and apparatus for formatting printer control signals. According to the invention, characters to be printed are stored in ASCII format in the memory of a microprocessor system. Successive characters are formatted into an on/off bit mapping where a bit signal corresponds to a blank region and a bit signal corresponds to a darkened region. Eight bit slices of the characters are formatted until an entire print width is completed and stored in an 8 bit.times.N buffer where N varies with the desired printer resolution. In the preferred embodiment two buffers are used so that while the contents of one buffer are used to control the printer the second buffer can be bit formatted under microprocessor control.

Abstract: In a digital printer, method and apparatus for formatting printer control signals. According to the invention, characters to be printed are stored in ASCII format in the memory of a microprocessor system. Successive characters are formatted into an on/off bit mapping where a bit signal corresponds to a blank region and a bit signal corresponds to a darkened region. Eight bit slices of the characters are formatted until an entire print width is completed and stored in an 8 bit.times.N buffer where N varies with the desired printer resolution. In the preferred embodiment two buffers are used so that while the contents of one buffer are used to control the printer the second buffer can be bit formatted under microprocessor control.

Abstract: An improved ink jet marking architecture for enhancing ink droplet placing accuracy. The improved architecture combines a bipolar scanning arrangement with a drop interlace scheme. The preferred marking apparatus comprises an array of ink jet column generators which direct ink droplets to first a charging region and then through a deflection region. The droplets are charged either negatively or positively depending on a desired droplet trajectory; thus the bipolar designation. The deflection region has an electric field strength slightly less than the breakdown field strength of air for the environment in which the apparatus is to operate. The high field strength reduces the charge which must be applied to the droplets and therefore minimizes the drop to drop coulomb interaction. The interlace strategy causes sequential drops from a given generator to be printed in non-sequential locations on the paper.

Abstract: A control system for controlling the size of the image produced by pixels generated by a raster scanner employing a binary rate multiplier for image size control along the X-axis, the multiplier being programmed to the size image desired to vary the frequency of the pixel clock signals output by the multiplier, together with a control flip-flop astride the image pixel stream and driven by the multiplier clock signals to speed up or reduce the rate at which image pixels are output. For image size control along the Y-axis, a phase lock loop is provided for controlling scanning carriage speed in response to the frequency of the signals output by a programmable frequency generator.

Abstract: An arrangement for optically reducing range finder effect in scanning systems employing plural image scanning arrays or a flying spot scanning beam. In the former, to reduce visually observable artifacts at the point where crossover is made from one adjoining array to the next due to misalignments of the scanning system components, field lenses are disposed between the system projection lenses and the document supporting platen. The field lenses serve to bend the imaging rays to a direction more nearly normal to the platen to thereby increase the depth of focus. Where the scanning system comprises a flying spot beam, a spherical mirror is disposed in the optical path to direct the imaging ray along an axis more nearly normal to the platen.

Abstract: Optical fibers are used to sense fluid ink drops along the x, y and z axis of an orthogonal coordinate system. A drop sensing zone is defined in the narrow space between the faces of a single input fiber and two output fibers. An LED infrared light source is coupled to a remote end of the input fiber. Infrared sensitive photodiodes are coupled to the remote ends of each output fiber. The photodiodes are in turn coupled to a differential amplifier whose output represents a displacement error for the x and y axis and represents a time reference for the z axis for the case where the drop flight path is along the z axis. A plurality of sensors are disclosed in an ink recording system having a plurality of nozzles and in an ink recording system having an ink generator traversing the length of a high speed rotating drum.

Abstract: An ink jet printer is disclosed employing a row of multiple ink jet nozzles aimed at a moving target or copy sheet. Each nozzle has a separate charging electrode associated with it but all the nozzles share a pair of common deflection plates that divert charged droplets over a shared gutter toward the target. Uncharged droplets go into the gutter. An electrostatic lens is shared by all the nozzles being positioned in the path of the charged droplets deflected toward the target. The lens aligns or focuses charged droplets from all the nozzles to a focus line on the target despite misalignment of nozzles relative to a print line on the target.

Abstract: An ink jet printer is disclosed of the type wherein a plurality of nozzles emit parallel streams of droplets toward a target. Each nozzle has a charging electrode to charge droplets selectively depending upon whether a particular droplet is intended for the target or a gutter. A pair of deflection plates span the paths of the droplet streams and deflects the charged droplets according to information to be printed. A multiple field electrostatic lens is used to align charged droplets from different nozzles to a common line on the target despite misalignments between nozzles relative to the common line.

Abstract: A system for processing halftone image data in digital format. The image data is electronically screened to provide a binary output suitable for storage or printing, the image data being processed in discrete blocks or cells. The error between actual and printed average gray values of each image cell processed is determined and the electronic screen thresholds are modified in accordance with such error (if any) prior to processing the next image cell. At the beginning of the aforesaid process and at the beginning of the processing each line, an error is randomly chosen.

Abstract: A line scanning apparatus employing a multiplicity of linear arrays, the linear extent of which is less than the length of the scan line. To permit an entire line to be covered, the arrays are offset from one another in the direction of scan with adjoining array ends overlapped. To correct for the misalignment and redundancy introduced, the image data from the arrays is buffered until a line is completed when readout, is initiated. During readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.

Abstract: A line scanning apparatus employing a multiplicity of linear arrays, the linear extent of which is less than the length of the scan line. To permit an entire line to be covered, the arrays are offset from one another in the direction of scan with adjoining array ends overlapped. To correct for the misalignment and redundancy introduced, the image data from the arrays is buffered until a line is completed when readout, is initiated. During readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.

Abstract: A line scanning apparatus employing a multiplicity of linear arrays, the linear extent of which is less than the length of the scan line. To permit an entire line to be covered, the arrays are offset from one another in the direction of scan with adjoining array ends overlapped. To correct for the misalignment and redundancy introduced, the image data from the arrays is buffered until a line is completed when readout, is initiated. During readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.

Abstract: A line scanning apparatus employing a multiplicity of linear arrays, the linear extent of which is less than the length of the scan line. To permit an entire line to be covered, the arrays are offset from one another in the direction of scan with adjoining array ends overlapped. To correct for the misalignment and redundancy introduced, the image data from the arrays is buffered until a line is completed when readout, is initiated. During readout, cross over from one array to the next is effected within the overlapped areas and the redundant data discarded.