High flux and high CRI may be achieved by combining different chips and/or phosphors. This, however, results in
inhomogeneous sources that, when combined with collimating optics, typically produce patterns with undesired artifacts.
These may be a combination of spatial, angular or color non-uniformities. In order to avoid these effects, there is a need
to mix the light source, both spatially and angularly. Diffusers can achieve this effect, but they also increase the etendue
(and reduce the brightness) of the resulting source, leading to optical systems of increased size and wider emission
The shell mixer is an optic comprised of many lenses on a shell covering the source. These lenses perform Kohler
integration to mix the emitted light, both spatially and angularly. Placing it on top of a multi-chip Lambertian light
source, the result is a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is
located in the same position with essentially the same size (so the average brightness is not increased). This virtual light
source can then be collimated using another optic, resulting in a homogeneous pattern without color separation.
Experimental measurements have shown optical efficiency of the shell of 94%, and highly homogeneous angular
intensity distribution of collimated beams, in good agreement with the ray-tracing simulations.