A light beam preparation arrangement includes a light tunnel, a rotatable unit, and a drive unit. In one aspect, a fixation rigidly attaches the light tunnel directly to the drive unit. In another aspect, temperature of the light tunnel in controlled. In another aspect, the rotatable unit is spaced a distance from the light tunnel, and the distance is controlled. In another aspect, alignment between the light tunnel and the rotatable unit is controlled. In another apsect, the light tunnel is hollow and a gas flows though the tunnel.