Abstract: Method and apparatus for converting gray-scale pixel information into data for rendering dots by a printer, video display, or similar device. A form of error diffusion is used wherein a thresholding error produced during the conversion process for a particular dot is propagated to one or more adjacent dots. The propagated error modifies the comparisons made for the adjacent dots and can be converted into lightness space to linearize the error. The error itself is modified when there is overlap of the propagating dot with an adjacent dot. The overlap modification is dependent upon the density levels being rendered and the amount of overlap between the dots.

Abstract: A weak electrostatic image on an imaging member is amplified by first toning it with charge injection toner. The imaging member is treated without fusing the toner image to reduce the charge injection inhibiting effect of charge associated with the toner imaging member interface. Subsequently to or simultaneously with said treating step the imaging member is charged positively, which charge injects through the toner to create an amplified electrostatic image that can be toned.

Abstract: A method and apparatus is provided for line scanning a beam receiving member, wherein a scanning beam is angularly or laterally displaced to compensate for potential scan line spacing error. The beam is displaced according to error arising from variation (flutter) in the relative motion of the beam and the beam receiving member, or according to error arising from movement of the receiving member while the scanning beam travels to a start of scan position, or both. Embodiments of beam displacement means include a row-addressable light valve array and an area-addressable light valve array.

Abstract: A system for converting gray-level input data into binary output data and efficiently preserve much of the original sharpness information. The input data is divided into halftone cells which correspond to several pixels in the original image information. The halftone cells are further divided into subcells which correspond to a plurality of pixels in the halftone cell. The subcells are thresholded with a matrix of threshold values to determine which binary pixels are to be rendered. Any error between the rendered pixels and the average density value of the subcell input values is propagated to adjacent subcells. The thresholding of the subcell pixels can use a separate threshold value for the individual pixels or can use an average threshold value for the entire subcell.

Abstract: A grey level non-impact recording apparatus and method provides data signals to a recording head having N recording elements per inch so that M sub-lines per inch can be recorded, wherein M is greater than N. In a specific example of a 400 dpi LED printhead, grey level data is sent to the printhead at a rate to record say 2400 lines per inch to provide a resolution of 400 dpi.times.2400 dpi grey level sub-pixels. Data from a data source may have a pixel resolution of 1/400".times.1/400" and the apparatus employs six sub-lines to record each of these pixels. The control for controlling the duration of recording of each LED for each sub-line includes a comparator which receives a grey level data signal at one input terminal and pulses representing a time changing count at another terminal. The count is produced by counter means and changes in response to signals from a clock means.

Abstract: Apparatus and method are described for copying with high productivity a mixed batch of originals containing for example process color originals accent color originals and/or single color originals such as black. A scanner scans the originals for color content and ascertains the number of image frames required to reproduce the original. Imaging is then only made on the number of image frames required for reproduction of that original. Scanning is performed with a relatively low resolution scanner. Thus, a "process" black original, made by the combination of three color toners, may be identified as black only even if the colors thereon are not perfectly registered. Such a black only original is reproduced using only one image frame and developed with black only toner thereby providing high productivity and improved quality over the original. The apparatus and method of the invention are preferably achieved using electrophotographic reproduction techniques.

Abstract: Method and apparatus for economically storing page data for reproduction by a high quality, color, gray-scale printer. A relatively large color value memory is used to store 24-bit color values for the entire page as they are received from the incoming data. The addresses of the color values are also stored in a pixel cell memory along with data which represents the sharpness or exact position of every pixel used to represent text/graphics images. A fixed number of memory bytes are used in the pixel cell memory to store both the sharpness data and the color value addresses for the multi-pixel area corresponding to the fixed number of bytes. In the event the large color memory becomes full of color values before the entire page has been stored, color values in a default memory are selected and addressed by the data stored in the cell memory. The default memory is much smaller than the main color memory.

Abstract: A multicolor reproduction is made by uniformly charging a photoconductive member, imagewise exposing that member to create a first electrostatic image, developing the first electrostatic image with a toner of a first color to create a first toner image, preferably uniformly recharging the photoconductive member, imagewise exposing the charged member creating a second electrostatic image, developing the second electrostatic image by the application of toner of a second color to the exposed areas. The process can be repeated for any number of colors. The multicolor image is then transferred in a single step to a receiving sheet. The second and subsequent development steps are carried out by a magnetic brush developing device employing hard magnetic carrier particles that are tumbled through a development zone which tumbling does not adversely affect the prior toner images.

Abstract: An LED printer apparatus or the like and method of controlling same is described wherein a sensor is provided at the focal plane of a lens means used to focus light from the LED's onto a film. This allows the sensor to provide corrections during actual printing operations. In response to the light sensed, adjustments are made by altering drive current to the LED's and/or changing the duration of an exposure period.

Abstract: An LED printhead includes an optical mask overlying the LED's to balance light outputs therefrom. The transmission density of the mask is adjusted for each LED in accordance with its respective light output to adjust same so that the light outputs from all LED's are the same. The mask comprises a UV fadeable dye whose transmission density is adjusted with a UV laser or other light source while monitoring the light output from the respective LED. The transmission density of the mask may be adjusted by a UV light source provided on the printhead during periods of nonuse of the printhead or the printhead may be removed from the recording apparatus for adjustment.

Abstract: An LED printhead includes an optical mask overlying the LED's to balance light outputs therefrom. The transmission density of the mask is adjusted for each LED in accordance with its respective light output to adjust same so that the light outputs from all LED's are the same. The mask comprises a micro-lenslet incorporating a UV fadeable dye whose transmission density is adjusted with a UV laser or other light source while monitoring the light output from the respective LED. The transmission density of the mask may be adjusted by a UV light source provided on the printhead during periods of nonuse of the printhead or the printhead may be removed from the recording apparatus for adjustment. The micro-lenslet is formed by depositing a liquid polymeric binder in droplet form over the LED and having same set to form the lenslet in situ.

Abstract: False contouring of a screened halftone image without including more sub-elements in each cell, increasing the size of each cell, or decreasing the screen frequency of the image is accomplished by assigning to each sequential sub-element of a halftone cell a weighted probability of being "ON" in accordance with the value of the associated input signal.

Abstract: While the human eye does not respond linearly to density and luminance changes, it does respond linearly to lightness L*. Equal increments on the L* scale do represent approximately equal steps in the perceived lightness of related colors. Near uniform color scales are available wherein equal differences in the color co-ordinates correspond to roughly equal visual differences. Accordingly, the disclosure relates to a visual-based process control method for copiers and printers which is based on a near uniform human visual response space rather than a density space. This gives a better control on the average for minimizing error in the human visual space than if the density space is used.

Abstract: An LED printer includes a gradient index lens array for focusing light from the LED's onto an image recording surface positioned at the image plane of the lens. A diffusion plate such as a ground glass plate is placed at the object plane of the lens array. Light from the LED's are slightly diffused by the ground glass plate and improved overlap of exposed pixels results. In one embodiment of the invention, the LED's are mounted on the plate on a "flip-chip" arrangement.

Abstract: False contouring of a screened halftone image without including more sub-elements in each cell, increasing the size of each cell, or decreasing the screen frequency of the image is accomplished by assigning to each sequential sub-element of a halftone cell a weighted probability of being "ON" in accordance with the value of the associated input signal. The weighted probability signal is converted to a binary value without a real time random number generator by a memory device having a plurality of rows, wherein each row represents a different probability that a sub-element will be "ON". The rows are accessed on the basis of the weighted probability of a sub-element being "ON".

Abstract: An improved printer apparatus includes a print head having a series of point-like radiation sources, such as LED's, arranged in a row for exposing a recording medium. Logic means is provided for determining which of the point-like radiation sources are to be selected for energization. A current driver means responsive to the logic means provides electrical current to the radiation sources selected. A current driver means include a current mirror having a master circuit for generating a reference current and a plurality of slave circuits for providing respective driver currents to the radiation sources selected for energization. The master circuit includes a resistor of the type that at least prior to adjustment permits for substantially continuous adjustment of driver current over a range of resistance values.Two independent power supplies are provided to the print head. One power supply provides electrical energy for the logic device at a fixed voltage suitable for the logic devices.

Abstract: Streaming magnetic tape system used as an electronic recirculating feeder for copiers and printers. Scanned and digitized original pages are stored on tape by high speed thin film parallel heads. The tape is reversed and the heads are shifted after one-half of the pages are stored on the tape. Storage of the second half of the pages results in the tape being back at the place of beginning, thus eliminating time-consuming rewinds. In one embodiment, the pages are counted before recording to ascertain the middle tape reversal location.

Abstract: Modular optical LED printhead arranged for a fixed focus distance outside the printhead structure. A supporting and registration plate contains a rectangular opening in which the lens is located. The plate is secured to the overall LED supporting structure of the printhead by end members which, with side members, completely seal the LED's and connections from contaminants. The registration plate has at least two surfaces thereon which mate with surfaces in the associated apparatus to accurately position the plate. During the alignment process of the printhead, the lens and plate are adjusted to provide a focus at a fixed distance from one of the registration surfaces of the plate. Alignment of the lens across the axis of the LED array is provided by recessed set screws and a shim. Because of the fixed distance from the registration surface, the printhead can be installed in suitably constructed apparatus without further alignment.

Abstract: A nonimpact print apparatus employing, for example, a printhead comprising a bank of light emitting diodes (LED's) provides correction for nonuniformities in light output of the LED's. A binary type of driver is provided for activating each LED in response to the presence of a data bit and a strobe pulse determines the period of activation. Certain LED's are additionally activated both before and after data activation using respective strobe pulses for correction for relative differences in emissions between such LED's and other LED's not requiring correction. The use of correction pulses prior to and subsequent to activation for the data pixel provides for more symmetrical exposure corrected dot-like image elements.

Abstract: A reproduction apparatus includes a plurality of recording elements, for exampl, LED's, arranged in a row along the length of the printhead. An image scanner scans an original document sheet to generate data signals related to the information on the sheet. In rasterizing the data for reproduction by the printhead upon a photoreceptor, means are provided for locating a pictorial portion on the document sheet which will require screening during the reproduction process. Image information comprising text and charts not in the area determined to include the pictorial information is reproduced at a resolution of N.times.M dots per square inch. Image information including text, etc., in the area determined to include the pictorial information is reproduced at N.times.(L.times.M) dots per square inch. The apparatus also includes means for providing additional emissions of the light emitting diodes, in response to photoreceptor travel, for correcting for nonuniformities in emissions of the LED's.