Resumen de Spectral control methods and applications for multi-channel led light engines
Lighting installations are usually static and based on long-standing visual indicators such as colour temperature, colour rendering, and illuminance values. However, we now know that spectral variations in light elicit non-visual effects via a distinct pathway in our brain, and it is important for designers and architects to take these into account: light influences our mood, modulates our attention, can suppress the production of melatonin and can shift our circadian rhythms. Considering all the spectral aspects of light is the initial step towards designing healthier environments that are both pleasant and respectful to our biology.
Multi-channel LED light engines can provide the core technology for a truly spectral lighting design, thereby enabling wider applications of light with different purposes.
This dissertation aims at facilitating this transition by delivering cost-effective multi-channel LED light engines capable of generating arbitrary spectral shapes. In the first part of this work, we develop a light engine for a research-oriented market and explore novel designs and solutions for an advanced industrial device aimed at tackling a more general lighting market. These two efforts led to the development of two optically and spectrally different devices: the SPECTRA TUNE LAB light engine (with an on-board spectrometer and ten different LED channels), and the VEGA 07 light engine (equipped with a colour sensor and seven different LED channels).
Second, to generate arbitrary spectral shapes, we perform an extensive study on different heuristic algorithms implemented directly in the microcontroller of the light engine as well as in its control software. We show that the simulated annealing algorithm provides fast computation times with excellent spectral fidelity.
Third, we develop two types of optical feedback controllers with different light sensors to prevent temperature-driven colour and spectral shifts, and the wear-out of the LEDs. Both these sensors, i.e. the spectrometer in the SPECTRA TUNE LAB and the colour sensor in the VEGA 07, are used to ensure high precision and accuracy of the emitted light at all times and for any kind of target spectrum.
Finally, we demonstrate the ways in which these devices can be used for different applications, thereby verifying the huge advantages and added value of this technology as compared to traditional lighting systems. Our developed light engines were installed in the intensive care units of two hospitals (Hospital Vall d'Hebron and Hospital Clínic in Barcelona), in office settings (ARUP's office in London), and 24/7 control rooms (Repsol's refinery control room in Tarragona), among others.
