Abstract: An improved printer apparatus includes a print head having a series of point-like radiation sources, such as LED's, arranged in a row for exposing a recording medium. Logic means is provided for determining which of the point-like radiation sources are to be selected for energization. A current driver means responsive to the logic means provides electrical current to the radiation sources selected. A current driver means include a current mirror having a master circuit for generating a reference current and a plurality of slave circuits for providing respective driver currents to the radiation sources selected for energization. The master circuit includes a resistor of the type that at least prior to adjustment permits for substantially continuous adjustment of driver current over a range of resistance values. Two independent power supplies are provided to the print head. One power supply provides electrical energy for the logic device at a fixed voltage suitable for the logic devices.

Abstract: A dot printer apparatus having a recording head with a plurality of recording elements such as LED's, etc. Counting means is provided to count the number of prior activations of each recording element during a past production run. In one embodiment, the recording elements are enabled during a nonproduction run to age those recording elements to compensate for their relative lack of use during the last production run. In another embodiment, age compensation is provided during the next production run with the on-times to the recording elements adjusted in accordance with correction signals related to the counting of prior activations of each of the recording elements during the last production run.

Abstract: Apparatus and method for electrophotographically producing high quality reproductions which contain different content types. Photoconductor image sectors are subjected to separate optical exposures selected for (1) good tone-scale reproduction of continuous-tone image portions and (2) high-contrast reproduction of line-type image portions. Photoconductor background area, which border continuous-tone image portions, are discharged to a level below the system's development level. Color line-art from a black and white original is also provided for in a color-copier by exposing a separate original containing a swatch of the color to be reproduced on the same image frames exposed to the image of the line-art. A digitizing tablet is used in combination with a selective erase means to provide selective screening and/or spot color effects. The digitizing tablet may be incorporated to use the exposure platen and may be of the sonic type or other types not employing grid lines visible to the photoconductor.

Abstract: A multicolor electrophotographic reproduction apparatus and method are provided for reproducing a copy in a selected colors. The apparatus includes a digitizer for inputting information denoting the location(s) of the pictorial information and the location(s) for which selected coloration is desired. The respective colors desired for reproduction of the information may be chosen from a menu of twenty-five or more colors stored in memory. In addition to an exposure source for reproducing an image of the original upon a photoconductor the apparatus also includes an illumination source for selective erase and a second illumination source which illuminates the photoconductor through a halftone screen to control the charge level on areas of a color separation image frame in accordance with the color selected to thereby effect the color which a reproduction will have.

Abstract: A circuit for generating a set of center pulse-width modulated waveforms comprises a counter having a time changing count, and comparators which compare the count with respective preset counts. The preset counts to the comparators being set so that the set of waveforms created is center pulse-width modulated.

Abstract: In a non-impact dot printer, such as an LED printer, multiple bits of image data determining the on-time of each LED are latched into an appropriate data register in accordance with a token bit that is passed along a shift register. The shift register is preferably bi-directional to permit for selection of direction wherein identical driver circuitry is provided on opposite sides of a line of LED's.