Production of screen printing blocks

Abstract

A method for producing half-tone reproductions such as printing blocks or color separators of an original on a recording medium by means of a recording element using rotated screens having any screen angle and any screen line spacing and being formed of periodically repeated, adjacent screen grid elements comprising screen dots varying in size with the tone values of the original. The recording medium has co-ordinated with it an UV co-ordinate system directed in the line direction and an XY co-ordinate system turned through the screen angle, both co-ordinate systems being subdivided into areal elements from which picture half-tone dots to be produced are collated. Notwithstanding the screen angle, screen threshold values are associated with areal elements of a matrix of limited scanning pattern range which corresponds to at least one screen grid element of the screen which is to be recorded. During the recording operation, the UV locus co-ordinates of the areal elements momentarily traversed by the recording element are recalculated in the form of the corresponding XY locus co-ordinates of the limited scanning range of the matrix and the screen threshold values associated with the XY locus co-ordinates determined are 'called up' from the matrix. A control signal which determines whether the areal element in question is or is not recorded on the recording medium is generated for the recording element by a current comparison of the screen threshold values called up with an image signal obtained by scanning the original.