Illumination apparatus

An illumination apparatus, comprising:

• a plurality of LEDs, the plurality of LEDs being arranged in an LED array, wherein the LEDs of the plurality of LEDs are micro-LEDs;
• a catadioptric optical structure aligned with the LEDs of the plurality of LEDs to provide a directional light output distribution, the directional light output distribution being of light output from the LEDs of the plurality of LEDs;
• wherein the catadioptric optical structure comprises a plurality of catadioptric optical elements arranged in a catadioptric optical element array, each of the catadioptric optical elements of the plurality of catadioptric optical elements aligned in correspondence with a respective one or more of the LEDs of the plurality of LEDs, each of the LEDs of the plurality of LEDs being aligned with only a respective one of the catadioptric optical elements of the catadioptric optical structure;
• wherein each of the plurality of catadioptric optical elements comprises in at least one catadioptric cross-sectional plane through its optical axis:
• a first cross-sectional outer interface and a second cross-sectional outer interface facing the first cross-sectional outer interface;
• wherein the first and second cross-sectional outer interfaces each comprise curved interfaces comprising first and second outer interface regions;
• wherein the first and second cross-sectional outer interfaces extend from a first end of the catadioptric optical element to a second end of the catadioptric optical element, the second end of the catadioptric optical element facing the first end of the catadioptric element;
• wherein the distance between the first and second cross-sectional outer interfaces at the first end of the catadioptric optical element is less than the distance between the first and second cross-sectional outer interfaces at the second end of the catadioptric optical element;
• and
• at least one transparent inner interface arranged between the first and second ends and between the first and second outer interfaces;
• wherein the catadioptric optical structure comprises:
• (i) a first transparent non-gaseous material with a first refractive index arranged between the first and second cross-sectional outer interfaces and the at least one transparent inner interface and between the first and second end of each of the catadioptric optical elements;
• (ii) a second transparent non-gaseous material with a second refractive index lower than the first refractive index arranged between a respective aligned LED and the transparent inner interface of each of the catadioptric optical elements;
• (iii) a third transparent non-gaseous material with a third refractive index lower than the first refractive index arranged between the first cross-sectional outer interface of a first catadioptric optical element and the second cross-sectional outer interface of an adjacent catadioptric optical element of the plurality of catadioptric optical elements and between the first and second end of each of the catadioptric optical elements;
• wherein a tilt angle with respect to the optical axis of an interface normal of each of the first and second cross-sectional outer interfaces varies continuously with the distance from the first end towards the second end;
• and a derivative of the tilt angle with respect to distance from the optical axis has a discontinuity at a boundary between the respective first and second outer interface regions of the first and second cross-sectional outer interfaces.