Abstract: Method for shading one of a first plurality of sensing elements of an optical sensor. High-reflectivity and low-reflectivity reference values of the output signal of each of a second plurality of sensing elements of the sensor are obtained. An average or nominal high-reflectivity value of the high-reflectivity reference values for each sensing element of the second plurality is calculated. An average or nominal low-reflectivity value of the low-reflectivity reference values for each sensing element of the second plurality is calculated. An offset value for one of the sensing elements of the first plurality is calculated using at least the average or nominal high-reflectivity values and the average or nominal low-reflectivity values. The one sensing element of the first plurality is calibrated using at least the calculated offset value. In one example, the first plurality and the second plurality are identical.

Abstract: Image data is corrected in a device or system using multiple halftones by predicting a second tone transfer curve corresponding to a second halftone based on a first tone transfer curve corresponding to a first halftone. First and second tone transfer curve compensate for application of the first halftone and the second halftone, respectively, to image data. The first tone transfer curve is determined by measuring image data halftoned with the first halftone and developing a first tone transfer curve that linearizes the measured image data. To produce the second tone transfer response curve, measured values of image data halftoned with the second halftone are estimated based on a predetermined relationship between the measured image data that is halftoned with the first halftone and image data that is halftoned with the second halftone. The second tone transfer curve is then developed as the curve that linearizes the estimated measured values of image data halftoned with the second halftone.

Abstract: A printer having a print engine (13) and a bit map memory (12) including a number of page image areas (31) into which information to be printed is rasterized and from which information for the print engine is serialized. A digital processor (11) controlling the print engine is operable to reduce a page image area (31) to a modified page image area (37) based upon the highest and lowest addresses at which information has been written into the page image area. The digital processor (11) is also operable to begin rasterization of a new page image area when a sufficient amount of an existing page image area (41) has been serialized to make available the requisite bit map memory for the new page.

Abstract: Heat accumulation in a thermal printhead is controlled by printing blocks of data along the print line in two passes when examination of the data shows the potential of excessive heating. The proportion of heat intensive or black parts in each block is determined by data processor 17 by examining the data for a line in memory 19. An accumulation is made assigning blocks having high heat density minus 2, blocks having intermediate heat density minus 1 and blocks having low heat density plus 1. When that figure is at minus two the next block is not printed until a second pass and the accumulation is set to zero. Where the accumulation is minus 1, print power is reduced for the next block, which is printed in the first pass. Excessive heat in the printhead results in machine damage and impaired print quality. A second pass is completely avoided where the data is such that this is unnecessary.

Abstract: Wear on the elements (5) of a printhead (3) is spread by shifting the region of use of the printhead line by line. Font (13) provides information as to whether any character in a line employs the upper three pels or the bottom three pels of a line. For each line which can be printed from different shift positions of the printhead, selection logic controls paper feed (15) to index platen (9) to the least used of a shifted position of printhead. Only those electrodes over the print line in each shifted position are used for printing. This distributes wear without requiring any special ribbon feed. The three pel height is at least as wide as the serifs on most characters, which avoids some electrodes being used for the serifs of given characters in more than one shift position.