Abstract: The present invention is a method and apparatus to minimize and prevent blooming problems in color image systems. Particular applicability is found where an image on image system is employed. The invention is inserted into the colorant driving signal path of the system. The invention places an averaging circuit in the path of one or more colorant driving signal streams. The averaging circuit produces an average value signal representative of a small area of its respective colorant. A modulator or other signal varying device responsive to the average value signal is placed in the path of yet another but separate colorant driving signal stream. In this manner the separate colorant driving signal is modulated or varied in response to the average neighboring value of a different color thus minimizing and preventing image blooming.

Abstract: A method for calibrating a multi-chip image sensor, and an imaging system having a multi-chip sensor that includes color correction factors generated by such a method. The image sensor is successively controlled to image three different test targets. After imaging each target, a set of correction factors is generated and used to correct image signals generated when imaging the next test target. A first set of correction factors corrects for pixel-to-pixel variations between imaging elements in the array. The second set of correction factors corrects for chip-to-chip variations between chips in the array. The third set of correction factors corrects for array-wide variations compared to a standard color chart.

Abstract: An encoding/compression technique using a combination of predictive coding and run length encoding allows for efficient compression of images produced by error diffusion.

Abstract: The present invention is a method and apparatus for resolution enhancement of gray-scale input images including text and line art, and more particularly to a filtering method and image processing apparatus for enhancement of high contrast line edges found in continuous tone (gray-scale) images without requiring that the input image data include predetermined tag bits to identify region types (e.g., continuous tone or text and line art).

Abstract: The present invention is a method and apparatus for reducing two-color moire often found during the rendering of full color images using halftoning techniques. The invention relies upon the application of a non-periodic halftone operation to the least perceptible color separation (e.g., yellow) so as to prevent the formation of periodic structures due to the interaction of the yellow colorant with one of the other colorants (e.g., cyan or magenta).

Abstract: The present invention is a method and apparatus for generating N-bit per pixel output signals in response to M-bit per pixel image input signals, where M is greater than N. The invention employs a halftone cell threshold memory that stores a single threshold for each cell element. During real-time processing of the video image signals, multiple thresholds are calculated based upon the stored thresholds, and the image signals are compared to the thresholds. The threshold calculation process is simplified by using equally spaced constants and any desired variation from the resulting equally spaced thresholds is accomplished through a remapping of the video image signals using a look-up table. The output of the plurality of comparisons carried out for each halftone cell element is then encoded to produce a digital gray-scale output signal.

Abstract: A method and apparatus for converting the resolution of an input image to a higher resolution that is a noninteger multiple of the input resolution. The method and apparatus employ either an interlocked or noninterlocked clustering arrangement of output pixels in order to assign to each output pixel a reference value determined from the signal levels of the input image. In addition, the method and apparatus include a template-based enhancement filter to further refine modify or alter the assigned signal level prior to its output as a higher resolution image.

Abstract: The present invention is a method and apparatus for detecting the presence of image regions requiring compact dot growth control and controlling the dot growth of such regions when rendered on a printing system. The invention operates to recognize those pixels within a bitmap image that are appropriate for alteration, using a template-based approach, and then alters the exposure pulse of identified pixels during imaging so as to assure a more stable output by a xerographic development system.

Abstract: A method of arbitrary image resolution conversion takes an original print ready image at a first resolution and orientation and simulates printing of that image by creating a representation of a page at a particular resolution and orientation using a suitable spot model for the reconstruction function. The image is then filtered with a low pass filter and sampled with an aperture that corresponds to the desired output. The image data, which may be definable at several bits per pixel, is then made print-ready by reducing the number of bits defining each pixel to a valid output state. The reduction step is accomplished through error diffusion methods that maintain the local area gray density level. The filtering step reduces moire in the converted image.

Abstract: The present invention is a method and apparatus for the enhancement of 1 bit per pixel image signals to produce a multiple-bit per pixel form. A binary input image is passed through a plurality of filters to generate level slices. The filters are stack filters implemented as look-up table or template-based filters, morphological filters, or any similar binary-to-binary filters that could be used to generate level slices. Each of the N-1 filters is used to produce the slices, where N is the number of possible gray-scale levels desired in the output image. Once the slices are generated, the resulting binary image data therein is recombined, by adding or stacking, to produce the desired multiple-bit per pixel output.

Abstract: The present invention is a method and apparatus for the enhancement of 1 bit per pixel image signals to produce a multiple-bit per pixel form. A binary input image is passed through a plurality of filters to generate level slices. The filters are stack filters implemented as look-up table or template-based filters, morphological filters, or any similar binary-to-binary filters that could be used to generate level slices. Each of the N-1 filters is used to produce the slices, where N is the number of possible gray-scale levels desired in the output image. Once the slices are generated, the resulting binary image data therein is recombined, by adding or stacking, to produce the desired multiple-bit per pixel output.

Abstract: An image processing system for altering the size of an image represented by a plurality of input video signals including a controller for producing a scale factor and a scale factor valid signal. The controller also includes a padder which is used to increase the accuracy of the scale factor during the operation of the controller. The signals generated by the controller are passed to an interpolator suitable for producing an output signal as a function of one or more of the input video signals in response to the scale factor and scale factor valid signal.

Abstract: An apparatus for determining a background level of an image to be scanned. The apparatus builds a series of histograms of the image each corresponding to a line of the image, analyzes each of the histograms, and averages the results of the analysis, to continually update a background level during the scan of the image. The apparatus may be implemented with a simple architecture capable of operating at high speed.

Abstract: A scanner-printer of the type that scans and prints in blocks, each block consisting of a preset number of image lines, in which the block of lines scanned by the scanning array is larger than the block of lines printed by a printing array so that there is provided additional image scan lines before and after each block of image lines printed, the additional image scan lines providing image context data for use in processing image signals adjacent the boundaries between blocks of image lines.

Abstract: Method and apparatus to increase the range of correction of photosite offset and gain response. Each photosite is provided with a correction value for offset and gain response based on measured light intensity value, which is stored in memory. Each photosite correction value is also provided with an attribute value which indicates whether the correction values are to be used as stored, whether a shift of the values is appropriate, in accordance with a stored shift value, or whether the photosite is noncorrectable, and accordingly requires the implementation of a bad pixel routine. Depending on the attribute value, logic is enabled to vary the correction values in accordance with a stored routine for shifting the stored correction value, or implementing a bad pixel routine. If the attribute requires a shifted value, the correction value is shifted a number of places in accordance with a shift stored in the decoder, before it is applied.

Abstract: A method and apparatus for processing a scan line of image data, wherein image data from portions of the scan line is processed simultaneously along plural channels, each channel processing a portion of the image data, and provided with context information from an adjacent portion of the scan line. Context pixels are added at the trail edge of a first scan line portion, derived from the lead edge of a second scan line portion. In certain image processing requiring preceding and succeeding pixel context information, subsequent to processing, on correctly processing pixels are transferred for subsequent processing, and pixels at the trail edge of a first scan line portion, and the lead edge of a second scan line portion are not transferred, leaving complementary scan line portions.

Abstract: Method and apparatus for processing a stream of image pixel data to determine the presence of high frequency half-tone data. The arrangement applies the function ##EQU1## to a stream of image pixel data. The presence of minimums of .phi.(k) at times indicative of predetermined half-tone image frequencies is detected and an output signal indicative of the presence or absence of minimums at the predetermined half-tone image frequencies is provided. More particularly, the two's complement of the stream of image pixel data is added to each of a plurality of differently delayed signals derived from the original stream of image pixel data. The absolute value is taken of the resulting function. The signal is summed for a selected number of pixels, corrected for noise, and reviewed for minimums. Minimums occurring at selected positions in the pixel stream indicate certain frequencies of the data. An output is created based on frequency indications.

Abstract: Apparatus for removing residual charged particles from a charge retentive surface characterized by a particle removal roller and a detoning roller, the former of which is adapted to remove the residual particles from the charge retentive surface and the latter of which removes the particles transferred to the particle removal roller. The detoning roller comprises an array of conductive electrodes extending about the circumference thereof such that when a multi-phase power source is applied thereto a travelling electrostatic wave is generated which causes charged particles having a predetermined diameter and charge to be moved axially of the detoning roller towards one end thereof. The particles so moved represent toner devoid of paper debris. Thus they are suitable for reuse.

Abstract: Apparatus for purifying toner prior to its use in developing latent electrostatic images. An electrically biased roll supported in the developer housing contiguous at least one of the development rolls serves to attract paper debris from the toner contained in the toner carried by the developer roll. The roll is fabricated from a suitable insulating material and electrically biased in a manner suitable for attracting the paper debris contained in the toner. The roll is rotated and a scraper blade is provided for removing the debris therefrom. The debris so removed is allowed to fall into a toner catch tray which can be provided with an auger for moving it out of the tray to thereby increase the capacity of the system for debris removal.