A Review of Contemporary Issues With Temporal Light Modulation of Lighting Systems

Temporal light modulation (TLM) is defined as a temporal change in luminous or color quantities of a light source, resulting from fluctuations of the power supply. Research studies published during the past decade helped define new metrics describing well-known visual effects of TLM such as flicker and the stroboscopic effect. Other visual artifacts induced by TLM such as the phantom array effect are still under investigation to better understand their occurrence and visibility, especially when viewing modern types of LED modules and power supplies, used for instance in automotive lighting and in color-tunable decorative or entertainment lighting. With the advent of solid-state lighting, high levels of temporal light modulation and new types of waveforms exhibited by some LED lamps and luminaires have generated concerns among users and regulators, thereby motivating the establishment of new research, metrics, and standards. Limits have been set in regulations to protect people from undesirable effects. Below these limits, TLM can be used as a useful optical signature to facilitate remote sensing measurements of lighting systems and their obtrusive light components by lock-in detection techniques.