This disclosure describes illumination assemblies operable to generate a patterned illumination that maintain high contrast over a wide temperature range. An implementation of the illumination assembly can include an array of monochromatic light sources positioned on an illumination plane, first and second optical elements, and an exit aperture. A chief ray of each light source within the array of monochromatic light sources can substantially converge at an exit aperture. In such implementations light generated by the array of monochromatic light sources can be used efficiently.