Abstract: Growth and clustering of halftone dots is a drawback in the reproduction of halftoned continuous tone images on prior art recording materials. Certain thermographic materials show a local microdot shrink effect called negative cross-talk upon neighboring microdots when exposing a microdot. Exposing these materials according to the frequency modulated halftone data of an image results in better tone rendering and lower noise due to lower dot clustering or negative cross-talk characteristics.

Abstract: A frequency-modulation halftone screen and method that enable the use of relatively large frequency-modulation halftone dots, which have desirable reprographic characteristics, in combination with high resolution rendering of text, graphics, and boundary information in general.

Abstract: A halftone screen generator, a halftone screen and a method for making the halftone screen are described. The halftone screen has a screen angle and rulings that define the theoretical centers of gravity of the halftone dots. The actual centers of gravity of the halftone dots are displaced from the theoretical centers of gravity by the length and angle of random phase vectors. In one example, the positional displacement of the centers of gravity of the dots is dot size dependent in an inverse relationship. The shift in dot centers of gravity away from the theoretical centers of gravity defined by the halftone screen effectively breaks up screen "patterning" and avoids objectionable halftone "graininess".

Abstract: The invention relates to a method and an apparatus for copying transparencies to a light-sensitive material, the apparatus including an illuminator for illuminating the original, wherein the illuminator has a plurality of individually addressable pixels which can be switched to light or dark and which are controlled according to a raster image. The density values of the original are first determined with a predetermined spatial and gray-scale resolution and the raster image is subsequently generated from the density values of the original according to the error diffusion method.

Abstract: A halftone screen is presented for use in combination with reproduction devices that are capable of rendering more than two tone levels. The screen is optimized to minimize both tone and color shift in the presence of variations in the printing process. The intermediate density levels, which are assigned to a minority of the microdots within each halftone cell, are different within adjacent halftone cells. FIG.

Abstract: A method for generating a screened reproduction of a multiple tone image comprises the steps of autotypical or amplitude modulation screening the multiple tone image to obtain screened data representing tones of the multiple tone image in terms of halftone dots; reproducing the halftone dots on an imaging element by means of a scan-wise exposure by means of a laser or a LED, wherein in extreme regions of the tone scale the shape of the halftone dots is compact, characterized in that the halftone dots have a ratio of peripheral length to surface area which is minimal.

Abstract: A method for making a lithographic printing plate from an original containing multiple tones comprising the steps of frequency modulation screening the multiple image to obtain screened data representing tones of the multiple tone image in terms of halftone dots; reproducing the halftone dots on a lithographic printing plate precursor having a surface capable of being differentiated in ink accepting and ink repellant areas upon scanwise exposure and an optional development step, by means of a scanwise exposure, wherein the scanwise exposure for rendering a halftone dot is intensity modulated.

Abstract: A screening system comprises at least one screen of which the phase is tone or image level dependent. This tone dependent phase shift influences the rosette structure and can be used to improve the neutral balance and color fidelity in multi-color reproduction and to minimize the visibility of such rosette structures in highlight and shadow areas.

Abstract: A halftone screen and method for generating halftones representing a continuous tone image, wherein the number of halftone dots per unit area varies non-proportionally with the tone values utilized as inputs to the screening process. The method incorporates an implicit gradation compensation as part of the frequency modulation halftoning itself to correct for the additional tone gain due to recording, plate processing and/or printing, as well as aesthetic corrections. This implicit compensation has the advantage that no external compensation is required, thereby maintaining the number of tone values which can be rendered on a digital system. Finally, the implicit gradation compensation enables the combination of page elements rendered according to either "conventional" or "frequency-modulated" halftoning techniques with appropriate tone-matching.

Abstract: A screening system comprises at least one screen of which the phase is tone or image level dependent. This tone dependent phase shift influences the rosette structure and can be used to improve the neutral balance and colour fidelity in multi-colour reproduction and to minimise the visibility of such rosette structures in highlight and shadow areas.

Abstract: A method for generating a screened reproduction of a contone image comprises the steps of screening the contone image to obtain screened data representative for tones of the contone image and suitable for driving exposure of microdots on a radiation sensitive imaging element; exposing the microdots according to the screened data by at least one set or plurality (p) of radiation beams (b), characterized in that at a point in time (t) at least two radiation beams of the set of radiation beams impinge on a particular microdot (m) of a scanline (l). In particular is described a method for making a lithographic printing plate comprising the abovementioned steps.

Abstract: A halftone screen generator, halftone screen and a method for making the halftone screen are described. The halftone screen has a screen angle and rulings that define the theoretical centers of gravity of the halftone dots. The actual centers of gravity of the halftone dots are displaced from the theoretical centers of gravity by the length and angle of random phase vectors. In one example, the positional displacement of the centers of gravity of the dots is dot size dependent in an inverse relationship. The shift in dot centers of gravity away from the theoretical centers of gravity defined by the halftone screen effectively breaks up screen "patterning" and avoids objectionable halftone "graininess".

Abstract: In order to improve the printability of a periodic halftone screen, the amount of growth of the halftone dots in a halftone screen is modulated as a function of tone in a tone selective way that is different for at least two halftone dots.

Abstract: A method for generating a screened reproduction of a multiple tone image comprising the steps of frequency modulation screening the multiple tone image to obtain screened data representing tones of the multiple tone image in terms of halftone dots, reproducing the halftone dots on an imaging element by means of a scanwise exposure, characterized in that the scanwise exposure for rendering a halftone dot is time modulated.

Abstract: A method for generating a screened reproduction of a multiple tone image comprises the steps of frequency modulation or stochastic screening the multiple image to obtain screened data representing tones of the multiple tone image in terms of halftone dots; reproducing the halftone dots on an imaging element by means of a scanwise exposure, wherein the size or composition of the halftone dot is modulated, by varying the number of microdots (or rels) composing a halftone dot.

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: A screening system and method are disclosed for reproduction of images in printing. The screening angles that are used are close, but not identical to conventional screening angles. The reproduction is nevertheless Moire free by the fact that the deviations in angles from the conventional system are exactly offset by the deviations in line rulings. The screening system is particularly advantageous when used for combinations of screens with rational tangent angles. The Moire free combination of rational tangent screens can be rotated by a constant angle with the amount of rotation controlled in small increments.