Flux concentrators in integrating sphere experiments: potential for increased detector signal

Concentrators yield no increase in collected flux over bare detectors in integrating sphere applications where a large field of view is allowed but can provide meaningful increases in signal when the field of view must be limited. The correct concentrator to use is elliptical rather than parabolic. In calculations of sphere efficiency and correction factors, the detector–concentrator assembly should be treated as if it were the detector alone.