Design and development of an LED-artificial sunlight source system prototype capable of controlling relative spectral power distribution

Abstract

An artificial sunlight source system that is able to produce a spectral power distribution (SPD) approximating ground level sunlight (GLS) as well as arbitrarily modified SPDs would facilitate the investigation of living-organism responses in various light environments. A prototype of a light emitting diode (LED)-artificial sunlight source system was designed as a first step towards the development of such a system. The LED-artificial sunlight source system produces a relative SPD (composition of wavelengths) approximating GLS in a wavelength range of 400-900 nm by applying different voltages to LEDs with 32 different peak wavelengths (395 to 910 nm). The irradiance of the system is as low as less than one-tenth of GLS. In addition, the system can produce time-varying light in any order at time intervals greater than one second by preparing a series of sets of applying different voltages to LEDs. The configuration of the LED-artificial sunlight source system, the method used to produce the desired relative SPDs, and testing of the system are described herein. We also discuss necessary improvements to achieve an artificial sunlight source system that can produce an SPD approximating GLS.