Abstract: A method for controlling the density of microdots produced by a binary or multilevel electrophotographic device. In one example, the toner concentration in a two-component developing system is modified as to keep the toner charge Q/M approximately constant. The toner charge is indirectly assessed. This allows to achieve consistent output densities, irrespective of the environmental parameters, such as relative humidity and temperature.

Abstract: A method is disclosed for rendering monochrome or colored continuous tone images by a system having restricted continuous tone rendering capabilities, such as electrographic printers capable of printing more than two density levels on each addressable micro dot. A method for preferred halftone dot growth is described, starting from isolated dots arranged along base lines and auxiliary lines, evolving to high density lines along the base lines and approximating full continuous tone rendition for high density regions. Preferred arrangements for the orientation, spacing and absolute location of the base lines and auxiliary lines are disclosed and a method to generate preferred arrangements. A moire free combination of three halftone images is described for the reproduction of color images. A method to select a restricted set of energy levels to obtain linear reflectance response is disclosed. Halftone cells are arranged in supercells to improve the density resolution of the system.

Abstract: There is provided a device for direct electrostatic printing comprising a back electrode (105), a printhead structure (106), an array of printing apertures (107) in said printhead structure (106) through which a particle flow can be electrically modulated by a control electrode (106a), an image receiving substrate (109) travelling between said back electrode (105) and said printhead structure (106) in the direction of arrow A and toner delivery means (101), comprising a charged toner conveyer (103), the reference surface of said charged toner conveyer being placed at a distance B (in mm) from the front of said printhead structure (106), and a magnetic brush to provide charged toner on to the CTC, wherein the linear surface speed of the magnetic brush LSM has a specified minimal ratio versus the travelling speed LSS of the image receiving substrate, such that LSM/LSS.gtoreq.0.5.

Abstract: A method is disclosed for rendering monochrome or colored continuous tone images by a system having restricted continuous tone rendering capabilities, such as electrographic printers capable of printing more than two density levels on each addressable micro dot. A method for preferred halftone dot growth is described, starting from isolated dots arranged along base lines and auxiliary lines, evolving to high density lines along the base lines and approximating full continuous tone rendition for high density regions. Preferred arrangements for the orientation, spacing and absolute location of the base lines and auxiliary lines are disclosed and a method to generate preferred arrangements. A moire free combination of three halftone images is described for the reproduction of color images. A method to select a restricted set of energy levels to obtain linear reflectance response is disclosed. Halftone cells are arranged in supercells to improve the density resolution of the system.

Abstract: An apparatus for security printing of a document on a substrate, having a first and second side, comprising:i) means for feeding variable data in a predetermined digital format to printing stations,ii) at least two printing stations, for image-wise depositing, in accordance to the predetermined format of the variable data, toner particles on the substrate,iii) means for fusing the toner particles to the substrate, to form a fused toner image, characterized in thata) the apparatus comprises means for introducing security features in the document andb) the means for fusing the toner particles to the substrate comprise means for heating and melting the toner particles such that between the melting toner particles and the substrate a contact angle of at most 90.degree. is formed and leave at most 25 mg/m.sup.2 of an external releasing agent on the fused toner image.

Abstract: A method is provided for reproducing a continuous tone image by imagewise application of toner particles to a substrate comprising the following steps:partitioning a surface of the substrate in a plurality of disjunctive microdots;applying to at least one microdot at least two types of toner, having substantially the same chromaticity.Preferentially, for each toner type a large majority of microdots within a region comprising adjacent microdots, is supplied with either a high or low amount of toner, whereas the other microdots are supplied with a medium amount of toner, and more preferentially for at least one toner type the region comprises at least one microdot supplied with a high, another with a low and another with a medium amount of said toner.In a preferred embodiment the minimum number (N) of types of toner particles used in the method of this invention depends on the volume average size of the toner particles used.

Abstract: A method is disclosed for rendering monochrome or colored continuous tone images by a system having restricted continuous tone rendering capabilities, such as electrographic printers capable of printing more than two density levels on each addressable micro dot. A method for preferred halftone dot growth is described, starting from isolated dots arranged along base lines and auxiliary lines, evolving to high density lines along the base lines and approximating full continuous tone rendition for high density regions. Preferred arrangements for the orientation, spacing and absolute location of the base lines and auxiliary lines are disclosed and a method to generate preferred arrangements. A moire free combination of three halftone images is described for the reproduction of color images. A method to select a restricted set of energy levels to obtain linear reflectance response is disclosed. Halftone cells are arranged in supercells to improve the density resolution of the system.

Abstract: A method is described for the rendering of an image on a carrier by a rendering system having a restricted density resolution. A classic screening method for a binary rendering technique is extrapolated to a plurality of energy levels that belong to three classes: non-marking, non-stable and marking stable energy levels. For each class, specific rules must be respected, in order to obtain predictable results without density discontinuities on the carrier. The methods make full use of the spatial and density resolution of the rendering system in areas of high density and increase the reproducibility of low densities by giving up some spatial resolution in the lower density regions.

Abstract: Techniques for achieving high resolution, high-speed gray scale printing with binary spatial light modulators. A spatial light modulator array is divided into subarrays, and the subarrays are illuminated at various levels (510, 512, 514, 516) of a modulated light source. Additionally, each pixel (520) can be divided up into four phases and printed in phase pairs.