The present invention relates to an apparatus for creating a pattern on a workpiece sensitive to radiation, such as a photomask a display panel or a microoptical device. The apparatus comprises a source for emitting electromagnetic radiation, a spatial modulator having multitude of modulating elements (pixels), adapted to being illuminated by said radiation, and a projection system creating an image of the modulator on the workpiece. It further comprises an electronic data processing and delivery system receiving a digital description of the pattern to be written, extracting from it a sequence of partial patterns, converting said partial patterns to modulator signals, and feeding said signals to the modulator, a precision mechanical system for moving said workpiece and/or projection system relative to each other and an electronic control system coordinating the movement of the workpiece, the feeding of the signals to the modulator and the intensity of the radiation, so that said pattern is stitched together from the partial images created by the sequence of partial patterns. According to the invention the drive signals can set a modulating element to a number of states larger than two.