Fig. 4
The structure of the developed LED luminaire. a and b represent the semi-aperture size and the depth of the reflector, respectively; φcut represents the cut-off angle of the luminaire, (ul0, zl0) and (ur0, zr0) represent the initial points of the freeform lens and the aspheric reflector, respectively; (ul0, zl0) divides the surface of the lens into two parts: surface 1 (S1) and surface 2 (S2), the two surfaces are connected smoothly at the connecting point; φ, with subscript, or both superscript, denotes the angle that light ray makes with optical axis, Δφ and Δβ denote the angle increment of emitting and refractive light ray, respectively