New Computational Methodologies Enable Solid State Lighting to Measure and Self-Adjust Based on Conditions

Reported in the SPIE journal Optical Engineering, two computational methods combine to enable high spectral fidelity and short computational processing times for spectrally-tunable light sources

29 March 2019

Truly spectrally tunable light engines can generate arbitrary spectra

These four examples show the best fit (blue solid line) to daylight D65 (a), an incandescent spectrum (b), the Melanopic (c) and a white LED spectrum (d) (Ph-LED YAG) (dashed black lines) made by optimizing the weights of the 10 different channels of the LED light engine (colored dash-dot lines). In all cases the spectra were normalized and are shown in arbitrary units.

BELLINGHAM, Washington, USA and CARDIFF, UK - An article published in the SPIE journal Optical Engineering, "Arbitrary spectral matching using multi-LED lighting systems," marks a substantial advance in lighting science and technology. In their paper, the researchers announce a two-pronged approach to both measure and self-adjust the spectral power distributions (SPDs) of LED lighting systems. Their methodology demonstrates the system's ability to maintain consistency and stability over an extended period of time.

Solid State Lighting (SSL) can be used to enhance our vision, sleep patterns, and wellbeing. SSL benefits are evident across their wide use in residences and offices as well as across industrial and commercial sectors, including the ongoing development of applications in medicine, imaging, agriculture, communication, transportation, and museum lighting. Some of these applications require highly precise light spectra that don't produce optical power variations or shifts in color over time.

The open-access paper addresses two challenges: how to keep temperature changes and age-based deterioration from impacting a light emission's strength, consistency, and color, as well as providing a reliable, internal, self-monitoring method.

The authors use a fast-computation, high spectral fidelity algorithm to determine channel weights of a targeted SPD; in conjunction with that method, an internal microprocessor provides a closed-loop control system that monitors and corrects the spectral output, compensating for shifts due to temperature changes or LED wear and tear. The authors' use of a general framework for multi-channel SSL systems, ensures the universal applicability of their findings across different lighting technologies.

According to Optical Engineering Associate Editor, SPIE Senior Member, and U.S. Air Force Research Laboratory Technical Advisor Daniel A. LeMaster, the research showcases significant advances in terms of lighting technologies, "This method to monitor and quickly compensate for the colorimetric issues that arise from junction heating and LED aging will be of great utility in the global LED lighting market."

The article authors are Aleix Llenas, of the Catalonia Institute for Energy Research (IREC) and Ledmotive Technologies, Spain, and Josep Carreras, of Ledmotive Technologies.

Michael T. Eismann, an SPIE Fellow and senior scientist at the U.S. Air Force Research Lab, is the editor-in-chief of Optical Engineering. The journal is published in print and digitally by SPIE in the SPIE Digital Library, which contains more than 500,000 publications from SPIE journals, proceedings, and books, with approximately 18,000 new research papers added each year.

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