Abstract: Reproduction apparatus calibration is effected by rendering not only neutral density target patches but also a sampling of intentional off-neutral patches produced by selecting sets of red, green, and blue (and sometimes black) input code values for those patches which deviate from sets of values that would produce neutral densities. Then, by analyzing how the measured densities of all the patches change with changes in code values, the optimum set or sets of the three (or four) input code values, that when used together produce a desired set of aim neutral density patches in a single iteration, are determined.

Abstract: Reproduction apparatus is periodically calibrated using only one member of a group of receivers. A correction is applied for other members of the group based on their relative differences from the one member. The one member to be calibrated periodically is designated the “key” member. Whenever a new member of the group comes into the lab, it, along with the key member are calibrated. The ratios of the density outputs over the full exposure range are calculated and saved for the new member. Then, at each reproduction apparatus calibration, the density outputs for the key member are determined and the ratios of density outputs are applied to predict the corresponding density outputs of the other group members, as if they were being calibrated at the same time.

Abstract: Color digital image signals generated by scanning an original or by a computer color graphics application are converted to signals representing normalized cone response values based on a color adaptation model of the human visual system. The cone response values are normalized to the white point of the input color digital image. The normalized cone response values are denormalized to the viewer adaptation point of the output viewing conditions of the output medium. The denormalized cone response values are transformed to signals for reproducing the digital color image.

Abstract: A raster image processor for an all points addressable printer includes at least three digital computer controlled processing units arranged in a parallel processing pipe line. The first unit is a master processing unit that receives printing instructions and generates rendering commands. The record unit is connected to the first unit by a dedicated bus, and receives the rendering commands over the bus and generates bit maps corresponding to the rendering commands. The third unit is a memory unit connected to the second unit by a second dedicated bus, and receives the bit maps from the second unit and stores them in a page memory. All three units are connected by a communications and control bus for overall coordination of the units.

Abstract: In a high speed character generator of the type employing reduced font characters, the improvement wherein font parameters are contained in a random access memory that is addressed by a master processor and supplies the font parameters directly to a bit map character generator, that is, the font parameters bypass the master processor.

Abstract: A raster image processor for an all points addressable marking engine includes a page memory having a data input and a write enable input. Halftone tints are applied to bit maps of objects stored in the page memory by applying a tint bit pattern to the data input of the page memory while a bit pattern representing the object is being applied to the write enable input of the page memory. Halftoning of a continuous tone digital image is performed by sending a word of a mask character having a pattern of "1" bits to the write enable input, selecting a halftone bit pattern with the code value of a pixel in the digital image and sending a word from the selected bit pattern to the data input of the memory. Color digital halftoning is performed in a similar manner by halftoning each color component of a color digital image.

Abstract: A raster image processor for an all points addressable marking engine includes a page memory having a data input and a write enable input. Halftone tints are applied to bit maps of objects stored in the page memory by applying a tint bit pattern to the data input of the page memory while a bit pattern representing the object is being applied to the write enable input of the page memory. Prior to applying the object bit maps to the write enable input of the page memory, the object bit maps may be combined with a texture bit pattern or clipped by a window bit pattern.

Abstract: A light sensing device comprises a photoconductive layer overlaying an array of PN junction diodes integrated within a semiconductor substrate. When a voltage is applied to the device to reverse bias the diodes, the voltage divides across the device in accordance with the capacitance of capacitive elements formed by the photoconductive layer and the junction capacitance of the diodes. When light impinges on the device, charge transfers from the photoconductive layer and accumulates at the underlying junctions at a rate that is directly dependent on the intensity of light incident on the corresponding portion of the photoconductive layer. When a diode reverse breakdown voltage is reached, the corresponding diode conducts. This causes an increase in current through the device, thereby signaling that a desired localized exposure has been attained.