Optimal pruning for selecting LEDs to synthesize tunable illumination spectra

Abstract

Multi-channel light-emitting diode (LED) light sources have been developed for various applications in lighting, but especially for spectrum-tunable lighting. However, how to select the optimal combination of LEDs for these light sources is rarely discussed. Unlike the negative-pruning process which operates by removing LEDs from a set of available LEDs based on an unrealizable negative-coefficient criterion alone, the proposed pruning process removes LEDs so as to minimize the synthesis error. This method not only produces the same optimal set of LEDs as those identified by the full-search method but also suggests when using phosphor-converted LEDs is beneficial. It does this by investigating the trade-off between the full width half maximum of the LEDs and the number of LEDs.