US Patent 8016455 Optical device for creating an illumination window

An optical device for creating an illumination window includes radiation sources and an optical element. The optical element is arranged to create a substantially collimated radiation beam from radiation generated by the radiation sources, in which the radiation generated by the respective sources is substantially unmixed. The optical device further includes a first lens plate having first sub-lenses, in which each first sub-lens projects a part of the radiation beam at an illumination window, such that the projections of each first sub-lens at least partially overlap.