Abstract: A method of processing print data allowing for rendering bands of print data in parallel. A main processor (52) of a single-chip multiprocessor converts an incoming page of print data into paths. The paths are then converted to primitives and the primitives are rasterized using parallel processor (60, 62, 64, 66). The parallel processors (60, 62, 64, 66) work in concert with the main processor (52) such that bands of the final print image are rendered into a frame buffer (58) in parallel, allowing for faster and more efficient processing of print data.

Abstract: A method for compressing screened image data for printing. The data is generated by tiling an image with multi-pixel cells. The pixels within any one cell may or may not be rescanned to be better fit for compression. The method allows for selection between two compression paths, one which has no loss (24), the other which is lossy (26). Once the data is compressed, the information is stored in a buffer (16), then sent to the exposure module. If the lossy scheme is selected, a quantization factor (14) is used in compression that may be adjusted, depending upon feedback signals (18,20), to increase or decrease the compression.

Abstract: The present invention provides a method of ameliorating the effects of misalignment between modulator arrays, and a system using the same. The ability reduce the effects of misalignment allows multiple, smaller, more cost effective arrays to be used instead of one large array. This can reduce the manufacturing costs of the array, especially arrays that are produced using semiconductor manufacturing processes such as the digital micromirror device. To avoid visual artifacts caused by the misalignment of two or more modulator arrays 1702, 1704, the individual arrays 1702, 1704 are optically overlapped and a portion of the image 1706 is generated by both arrays 1702, 1704. A breakpoint is chosen between two pixels in the overlapped region 1706 at which to abut the images from each of the modulator arrays 1702, 1704. The breakpoint is changed each row of pixels to minimize the detectability of any visual artifact caused by misalignment between the modulator arrays 1702, 1704.

Abstract: A method of dynamically quantizing pixel data for use by a digital printer system that prints the pixel data with modulated pixel values. The data is first modulated, with the output pixel values being determined by an image screen. (FIGS. 1 and 2). Then, the data is quantized, using different quantization tables for different pixel values of the same image. The parameters that determine which quantization table is used for a particular pixel value include the pixel's position with respect to the screen or the pixel's image content. (FIGS. 3 and 5) In the case of data that is also being compressed with differential pulse code modulation, the quantization can be based on a buffer fullness measure (FIG. 6).

Abstract: A method for defect-correction printing. A spatial light modulator that is used to generate the image is mapped for defects. The ON defects are compensated by setting a background level that is equal to the cumulative exposure of the ON defects, and then this background level becomes the threshold for development by the electrophotographic process. The system compensates for OFF defects by allocating the bits and exposures necessary to approximate the OFF defects to operative elements, thereby keeping the cumulative exposure for that pixel in the final printed image exactly, or as closely as possible, equal to the desired exposure. The corrections are contained in a defect correction module (10) that generates the appropriate patterns with the correct allocations to minimize error.

Abstract: In classic optical rendering systems, the spot, illuminating a microdot on the photosensitive medium, is designed to overlap with neighboring microdots, typically having an overlap of 1.7 times the pitch of the microdots, for a luminous intensity of 1/e.sup.2 the highest intensity. A "sharp" photosensitive medium, such as a photographic film used in graphical applications, generates a binary circle, obtainable by thresholding. The area of such a circle is too large, which results in higher dot gain.Many systems, such as electrographic systems, do not behave as a "sharp" medium. If intermediate energy levels are used, in order to obtain continuous tone or multiple density levels, thresholding behavior may be avoided by appropriate choice of energy levels. Such a different sensitometry results in specific requirements for the energy distribution for each microdot.

Abstract: A method of reducing the effects of aliasing. Pixels are divided into phases, such that a phase or combination of phases may be printed to provide one of a number of dot shapes for each pixel. When a pixel is partly overlapped by an object to be printed, that pixel's dot shape is determined by determining which dot shape is the best geometrical match with the overlap. (FIGS. 3 and 7). Then, a greyscale value is determined for the selected dot shape by determining what greyscale will provide an effective greyscale that substantially corresponds to the percent of overlap by the object with the pixel. An alternative method selects a greyscale value for each phase rather than for the entire dot shape.

Abstract: A method of eliminating the effects of aliasing when printing objects having opposing edges. A center line between the opposing edges is identified. (FIG. 3). "Opposing pixels" on the edges are also identified and assigned offsetting grayscale values. (FIG. 4). This prevents the distances between the edges from appearing too narrow or too wide.

Abstract: An improved method of line screen printing. Instead of screening the image with only one set of lines, the image is also screened with a second set of lines, which are substantially orthogonal to those of the first set. (FIG. 3). The screening is accomplished with two types of cells, horizonal cells and vertical cells. The pixels are classified according to their distance from the nearest line in the horizontal cells. This process is repeated with respect to the vertical cells. (FIG. 5). Different tone curves, which map input pixel values to output pixel values, are associated with different pixel classifications. In general, pixels closer to lines have tone curves that map to higher output values. (FIGS. 6 and 7). Because each pixel is in both a horizontal cell and a vertical cell, each pixel has two values from the tone curves. For each pixel, its two tone curve values are combined to obtain a greyscale value for that pixel.

Abstract: A method for printing grayscale images that compensates for problems in the printing process. The presence of a defective element on a spatial light modulator (12) is compensated for using a background value. The background value is determined by the number of defective elements stuck in the ON position, and that value is added to all of the exposure values of the elements, creating exposure data. In one embodiment, a defect intensity value is subtracted from those pixel exposure values affected by defective elements. The exposure data is used to generate microimages on a photoreceptive drum, the data is decremented and the steps are repeated until an entire image has been produced.

Abstract: A method for printing grayscale images that compensates for problems in the printing process. The presence of a defective element on a spatial light modulator (12) is compensated for with use of a white balancing area. If a column of the modulator (12) has an element stuck ON, a corresponding element in the same column in the white balancing area is turned OFF while all other columns have elements that are ON. If the illumination is non-uniform, the exposure values of each element are multiplied by an efficiency factor which compensates for the non-uniformity.

Abstract: A method for printing grayscale images. A sliding window memory stores an array of exposure data. The memory is initialized (80) with zero values. The memory is then addressed (82) so that the last row of the array is filled with exposure data. A microimage is then generated based on the exposure data (84). The data in the array is then decremented (86). If the page to be printed is not completed, the array's addresses are rotated (82) so that the data for the first row drops out, the data for other rows is readdressed as the next row, and new data fills the last row.

Abstract: The present invention provides a method of ameliorating the effects of misalignment between modulator arrays, and a system using the same. The ability reduce the effects of misalignment allows multiple, smaller, more cost effective arrays to be used instead of one large array. This can reduce the manufacturing costs of the array, especially arrays that are produced using semiconductor manufacturing processes such as the digital micromirror device. To avoid visual artifacts caused by the misalignment of two or more modulator arrays 1702, 1704, the individual arrays 1702, 1704 are optically overlapped and a portion of the image 1706 is generated by both arrays 1702, 1704. A breakpoint is chosen between two pixels in the overlapped region 1706 at which to abut the images from each of the modulator arrays 1702, 1704. The breakpoint is changed each row of pixels to minimize the detectability of any visual artifact caused by misalignment between the modulator arrays 1702, 1704.

Abstract: An improved method for time delay and integration printing for gray scale. A gray scale represented by a bit pattern is provided for time delay and integration printing onto a photosensitive substrate. The pattern (12) is rotated about the light intensity cycle of the light source such that microbands in the final image are minimized or eliminated and sent to a spatial light modulator (10) for transfer to a printing substrate.

Abstract: A display system (20) that uses multiple SLMs (25) to enhance horizontal or vertical resolution, or both. For example, to approximate a two-fold increase in horizontal resolution, the input data is sampled at a doubled rate, and each SLM (25) receives every other sample. Each SLM (25) generates an image, and the two images are partially superposed with a horizontal offset and simultaneously displayed. The resulting output image has a perceived resolution that approximates that of an image generated by an SLM with twice as many pixels per row.

Abstract: A method and apparatus for printing stroke and contone data together are provided in which data to be printed (102) is identified by a processor (100) as being either stroke or contone data. For contone data, processor (100) controls a light source (14), a spatial light modulator (12), and an optical photoconductive drum (16) to generate image quality graphics by using spatial light modulation in the process and cross-process directions. For stroke data, processor (100) controls light source (14), spatial light modulator (12), and optical photoconductive drum (16) for high resolution printing by using intensity modulation. Processor (100) is operable to control light intensities through the use of lookup tables stored in a memory (104).

Abstract: A method and apparatus for spatial modulation in the cross-process direction. A spatial light modulator includes an array (12) of individual elements. Light from a light source (14) is reflected from these individual elements onto phases of pixels (20 and 54) of an organic photoconductive drum (16) thereby determining the gray shade of that pixel. The light from the individual elements may be focused through optics (18).