Light-emitting unit with fresnel optical system and light-emitting apparatus and display system using same

A light-emitting unit that emits substantially collimated and substantially uniform light, the light-emitting unit comprising:

• a support structure having a central support structure axis, an open front end that defines an output end, and an interior open at the open front end and defined by a bottom surface and at least one sidewall;
• a light source disposed on or adjacent the bottom surface and that emits divergent light;
• a single monolithic lens element arranged in the support structure interior, the lens element comprising:
• i) a central lens axis;
• ii) a lower surface adjacent and spaced apart from the light source and that receives the divergent light and forms therefrom first redirected light;
• and
• iii) an upper surface that resides at or adjacent the output end and that receives the first redirected light and forms therefrom second redirected light;
• the lower surface comprising a first microstructure that includes inner and outer regions that are defined by a normalized transition radius ρT in the range 0.6≤ρT≤0.8, wherein the first microstructure within the inner region only refracts the divergent light while the first microstructure within the outer region both refracts and totally-internally reflects the divergent light to form the first redirected light;
• and
• the upper surface comprising a second microstructure that receives the first redirected light and forms therefrom second redirected light that is substantially collimated and that has a radiant exitance that is uniform to within +/−8% of an average radiance exitance of the second redirected light.