LED Light Guides
Light guides are also known as light mixing rods, pipes or integrators. They are designed for any application that requires the homogenization of a light beam and therefore can be commonly found in stage lighting fixtures and automotive applications. Their mixing ability depends on the cross sections of entrance and exit surface as well as the length of the integrator. Due to periodic total internal reflections at the side surfaces a non-uniform source beam profile is folded several times leading to a uniform homogenization via superposition, regardless of the spectral characteristics. A stronger effect is gained with higher number of reflections. Typically, longer light guides are required for low numerical aperture (NA) sources, while shorter lengths are sufficient for homogenizing the light from high NA sources.
Example simulation data for the transmission of a square-shaped integrator depending on entrance diameter, exit diameter and length are shown in Fig. below.