To provide an inexpensive constitution of a double facet illumination system in which an illumination mode thereof can be variably controlled, and to provide a method for controlling the illumination mode in such an illumination system.

An illumination system IL of a lithographic apparatus includes a first optical element 100 comprising first raster elements 110 that divide radiation beam into a plurality of radiation channels, and a second optical element 160 to receive the plurality of radiation channels, the second optical element 160 comprising second raster elements 150. For each of the radiation channels, a raster element of the first raster elements is associated with respective raster elements of the second raster elements to provide a continuous beam path from the first optical element to an object plane. A filter SF is provided in a path through which the radiation beam has passed to create a desired spatial intensity distribution in a pupil of the illumination system IL.