A directional illumination apparatus comprises an array of micro-LEDs that may be organic LEDs (OLEDs) or inorganic LEDs and an aligned solid catadioptric micro-optic array arranged to provide a water vapour and oxygen barrier for the micro-LEDs as well as reduced sensitivity to thermal and pressure variations. The shape of the interfaces of the solid catadioptric micro-optic array is arranged to provide total internal reflection for light from the aligned micro-LEDs using known transparent materials. A thin and efficient illumination apparatus may be used for collimated illumination in environmental lighting, display backlighting or direct display.