Abstract: A security print contains a background pattern formed for example of dots or lines. An object, for example the text “BEWARE OF FORGERY”, is worked into this regular background pattern for copy protection. The text is worked in by the individual lines of the background pattern being split at the places where the text is located into two partial lines which are each only about half as wide as the original line. With the naked eye this split of the background pattern components is not, or barely, recognizable. When such an original security print is copied on a conventional copying machine the original, relatively wide lines of the background pattern appear on the copy but the partial lines formed by the split thereof are not, or very poorly, copied so that the text “BEWARE OF FORGERY” appears clearly in the copy.

Abstract: A laser engraving machine (4) is used for engraving a workpiece surface (22) by a modulated laser beam in order to form a desired profile in the workpiece surface. The fine structures of the profile are formed by the laser beam of a first laser which is modulated by an acoustooptic modulator (12) with relatively high modulation frequency, while the deep areas of the desired profile are formed by the laser beam of a second laser (10), for which purpose the modulator (12), on the one hand, and the second laser beam source (10), on the other hand, are driven by interrelated but separate control signals (S3, S2). The two perpendicular polarized laser beams from the modulator (12) and the second laser beam source (10) are transmitted and reflected by a selective mirror (14), respectively, and applied commonly via an optical system (18) to the workpiece surface (22) to be machined.