Metrology for temporal light modulation

The EU Ecodesign ‘Single Lighting Regulation’ aims to simplify market rules for LED lighting products, that if successfully applied could reduce power consumption in Europe by about 40 TWh in 2030. Applying from September 2021, its specifications include consideration for effects caused by rapid variations in LED brightness and spectral distribution, specifically flicker and stroboscopic effects. Flicker can induce perceptions of visual instability, while lighting fluctuations can elicit a ‘stroboscopic effect’, that affects perceptions of motion in dynamic environments for many people. Such ‘temporal’ effects can cause fatigue, trigger conditions like epilepsy or migraine, and cause other safety concerns. Not yet covered in the regulation is the phantom array effect, which can be caused by stationary lighting influencing the perception of shape or position of objects for observers in motion.

To demonstrate compliance with the new rules, the lighting industry, instrument manufacturers and market surveillance authorities must perform reliable, comparable measurements. However, the necessary metrology is not yet available and standardised metrics have not been entirely defined.

The project devised new measuring techniques based on high-resolution time-resolved and spatially-resolved imaging and contribute to standardisation. It investigated and delivered validated methods and measurement conditions of lighting characteristic of flicker and stroboscopic effects. A model of the phantom array effect, based on representative perception experiments, has also been developed. Stakeholders were then asked to participate in an inter-laboratory comparison of the methods and metrics developed for flicker and the stroboscopic effect.

New methods and metrics will help the automotive, entertainment and lighting industries quantify the significance of these effects and so support development of improved product safety and consumer appeal. Appropriate standardisation will also support compliance with regulations and support the phase-out of incandescent lighting, and so contribute to reduced carbon emissions across Europe.