Abstract: A rasterization method of patterns with periodic components for SLMs is presented, comprising obtaining (S10) of an original pattern, having a periodicity. A first pattern main period is determined (S21). Image area and a first pitch of imaged elements are obtained (S31). The original pattern is scaled (S41) by a first raster scaling factor. The scaled pattern is cropped (S51) to comprise a first integer number of repetitions of the pattern items presenting a periodicity in the first direction that is covered by the image area, giving a rasterized pattern adapted to the intended pattern generator. The rasterized pattern is associated with data representing the first scaling factor. A writing method comprises obtaining of the rasterized pattern. Elements of the SLM in the pattern generator falling outside the rasterized pattern are set to be disabled. The rasterized pattern is written with an optical scaling to a target surface.