Abstract: A method is disclosed for halftoning images either via a direct method or a threshold array construction. The method includes comparing a pattern to an image and calculating a first potential in order to determine a first set of pixels to move; calculating a second potential in order to determine a second set of pixels in which to move the first set of pixels; and then moving pixels in the first set of pixels having high first potentials to pixel locations in the second set of pixels having low second potentials. The method may further include an inner program loop that decreases the number of pixels to move in the first and second sets and iteratively repeats the above steps; and an outer program loop that resets the number of pixels moved in the first and second sets and iteratively repeating the process to further optimize the pattern.

Abstract: A method and system for performing enhanced error diffusion on a digital image is disclosed. The method and system include gathering statistics in a neighborhood of pixels around a current pixel to detect an amount of contrast in the neighborhood of pixels, and varying a threshold value in relation to the amount of detected contrast. According to the present invention, the amount of detected contrast is used to determine to what extent the neighborhood of pixels comprises an edge region or a non-edge region of the image in relation. Any distributed error assigned to the current pixel is added to the current pixel to obtain a new current pixel value. An output value for a pixel in the neighborhood of pixels is set based on whether the pixel value is less than, or greater or equal to, the threshold value.

Abstract: A technique combines most of the advantages of both blue noise and clustering in generating a partially clustered aperiodic mask and using it in a dither array algorithm for halftoning, such that the amount of clustering can be modulated. A method to create an enlarged partially clustered aperiodic dither mask, appearing as a modulated version of a periodic enlargement of original mask, is used when the original mask generates patterns that are not visually pleasing or the original mask doesn't generate enough distinct grey levels. The method of halftoning of grey scale images utilizes a pixel-by-pixel comparison of the image against a partially clustered aperiodic mask in which the clustered aperiodic mask is comprised of a partly random and partly deterministic single valued function which is designed to produce visually pleasing dot configurations when thresholded at any level of grey.

Abstract: A method, apparatus, and article of manufacture, for transmitting data to facsimile presentation device is disclosed. The method comprises the steps of receiving a presentation job comprising input data associable with at least one input grayscale value, retrieving one of a plurality of stored transforms, each transform for modifying grayscale commands to control a grayscale rendering characteristic of a presentation device associated with the transform, applying the transform to the input grayscale value to produce calibrated grayscale values, and transmitting data representing the calibrated grayscale value to the facsimile presentation device.

Abstract: A method, apparatus, article of manufacture for transmitting data to a facsimile presentation device is disclosed. In one embodiment of the invention, the method comprises the steps of receiving a presentation job comprising input data associable with at least one input grayscale value, retrieving at least one of a plurality of threshold matrices, each threshold matrix selected to control a grayscale rendering characteristic of the facsimile presentation device associated with the threshold matrix, applying the grayscale values to the retrieved threshold matrix to rasterize the input data, and transmitting the rasterized input data to the facsimile presentation device. This invention can be practiced in several embodiments, and permits the user to select the threshold matrix according to the presentation device and/or a selected presentation quality.

Abstract: A method that involves sweeping multiple beams for a plurality of sweeps. The multiple beams are modulated for the plurality of sweeps according to a test pattern. The test pattern has an associated vernier period and the vernier period corresponds to a wavelength. The wavelength is perceptible to the human eye. An apparatus having a printhead configured to produce multiple beams where the multiple beams are configured to be modulated according to a stored test pattern. The test pattern has an associated vernier period and the vernier period corresponds to a wavelength. The wavelength is perceptible to the human eye.

Abstract: A method, apparatus, and article of manufacture for configuring a first printer to print according to the grayscale printing characteristics of a second printer is described. The method comprises the steps of characterizing the grayscale printing characteristics of the first printer and the second printer, defining a transform between the grayscale printing characteristics of the first printer and of the second printer, and modifying the first printer threshold matrix in accordance with the transform. The article of manufacture comprises a computer-readable medium tangibly embodying the above described method steps. The apparatus comprises a scanner or densitometer for characterizing the grayscale printing characteristics of the first printer and the second printer, a processor for determining a transform between the grayscale printing characteristics of the first printer and those of the second printer, and for modifying the first printer threshold matrix in accordance with the transform.

Abstract: A method of generating artifact-free threshold matrices for digital printing devices is provided. The method includes, for example, the steps of establishing a threshold matrix by examining at least one color level for artifacts and removing the color level from the threshold matrix if it has artifacts. The method further includes the steps of examining a range of color levels for artifacts and removing the color levels from the threshold matrix which have artifacts and evenly distributing the remaining color levels over a range of color levels from a first color level to a last color. The examination of color levels for artifacts may be implemented manually or through an automated computer controlled process. The automated process includes digitally acquiring the color level and performing a Fourier transform on the color level to determine its spectral components. The spectral components are analyzed to determine the presence or absence of artifacts.

Abstract: A multiple laser beam scanning optical system for correcting monochromatic and polychromatic aberrations comprising a doublet cylindrical lens for receiving the multiple beams and directing them to a rotating polygonal mirror. Scanning lens means are located to receive the beams from the mirror and direct them to the image plane.

Abstract: This is an electronic scheme for correcting for mechanical misalignment and chromatic aberrations from laser beam to laser beam in the scan direction of a multiple beam laser scanning system for use in an electrophotographic machine. Each beam is first corrected for mechanical misalignment and thereafter for chromatic aberrations. A reference laser beam produces two pulses near the start of scan (SOS) and two pulses near the end of scan (EOS). A non-reference laser beam then produces SOS and EOS pulses from which the mechanical misalignment is calculated. A gated clock is energized by the reference pulse and a tapped delay line is used for nanosecond resolution.

Abstract: An optical system for use with laser chips to counteract variations in wavelength produced by semiconductor chips, to counteract astigmatism effects common to laser chips, to counteract variations in the distance between the plane of emission of the beam and the plane of a collimating lens, to counteract variations in beam size in perpendicular planes, to counteract variations in the divergence angle of emission common to laser chips, and to counteract tilt variations caused by imperfect reflecting surfaces. The system includes an apertured achromatic doublet lens for collimating the beam, a cylindrical lens, a rotating mirror, and a combination of toroidal and spherical lens.