In a partial image, certain image dots are deflected optically in x direction with reference to imaginary undeflected image dots, and the x deflection of an image dot is less than the length of the side of an image dot. The image is traced by a light-controlling unit (preferably a semiconductor chip with tilting-mirror elements) with light-controlling elements arranged similar to a matrix. A computer program loads the light-controlling unit with a control pattern for tracing each partial image.