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: 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.

Abstract: The invention provides electrophotographic apparatus for forming a subsequent toner image overlapping one or more toner images previously formed on a surface of an electrophotographic element.The apparatus includes means for electrically charging the surface and the previously formed toner image or images, and means for forming an electrostatic latent image overlapping the previously formed toner image or images on the surface by imagewise exposing the element, through the previously formed toner image or images. The latent image forming means provides actinic radiation of a wavelength outside the range of 400 to 700 nanometers with the density of the previously formed toner image or images to the actinic radiation being less than about 0.2. The apparatus further includes means for electrographically developing the electrostatic latent image to thereby form the subsequent toner image.

Abstract: In plural-stage liquid development of electrostatic charge patterns, as in multicolor electro-photography, image defects occur in areas of the image which are undeveloped or background areas of a previous development stage. The method of the invention avoids such defects by rinsing the image with a polar liquid between development stages to remove counterions which are believed to cause the defects.

Abstract: The invention provides an electrophotographic method of forming a subsequent toner image overlapping one or more toner images previously formed on a surface of an electrophotographic element.The method comprises the steps of:(a) electrically charging the surface and the previously formed toner image or images,(b) forming an electrostatic latent image overlapping the previously formed toner image or images on the surface by imagewise exposing the element, through the previously formed toner image or images, to actinic radiation of a wavelength outside the range of 400 to 700 nanometers; the density of the previously formed toner image or images to the actinic radiation being less than about 0.2, and(c) electrographically developing the electrostatic latent image to thereby form the subsequent toner image.

Abstract: An electrophotographic proofing element is described comprising a photoconductive layer on an electrically conducting substrate, capable of transmitting actinic radiation to which the photoconductive layer is responsive, and a dielectric support, releasably adhered to the substrate, comprising the photoconductive layer or an overcoat thereof forming a surface of the element capable of holding an applied electrostatic charge. To use the element, the surface of the dielectric support is charged, and the photoconductive layer is imagewise-exposed to actinic radiation, thereby forming a developable electrostatic image on the dielectric surface. The electrostatic image, in turn, is developed with toner to form a first color image. A composite color image is formed on the element by repeating the sequence one or more times with imagewise exposure of the photoconductive layer to actinic radiation transmitted through the transparent support, and developing over each preceding image with a different color toner.

Abstract: Apparatus is disclosed for softening and displacing electrically insulative material on a portion of the surface of an electrographic imaging web by heat and pressure to effect electrical contact (e.g. grounding) with an isolated conductive layer thereof. One apparatus embodiment maintains a constant tension in the web which urges the insulative material into pressure contact with flanges on each end of a heated aluminum roller. The roller makes electrical contact with a conductive layer of the web when the softened insulative material is displaced from between the roller and the conductive layer. Means for protecting the center of the web from the heat supplied to the roller and means for preventing a buildup of insulative material on the flanges of the roller are disclosed.

Abstract: Image defects in liquid-developed photoconductive film, which before use has been stored in roll form at elevated temperature, are corrected by an on-line treatment of the film prior to development. The method comprises heating the photoconductive film prior to charging while under stress-relieving tension and then cooling it.

Abstract: A method for amplifying an electrostatic, charge-differential pattern is disclosed. The method comprises (a) imagewise forming a first toner deposit by developing a first electrostatic pattern having a first charge differential per unit area whose maximum value is no greater than a preselected level, (b) in an image-amplification element comprising a charge-holding surface layer overlying a field-supporting electrode, forming a current-carrying path between the toner deposit and the field-supporting electrode, (c) under conditions in which nontoned regions are not photoexcited, overall charging the image-amplification element with sufficient charge to form an enhanced electrostatic charge pattern having a second charge differential per unit area whose maximum value is greater than the preselected value in step (a), and (d) developing the enhanced charge pattern into a second toner deposit.