Enabling Unique Photonic Markers for Visible Light Sensing

Backscattered Visible Light Sensing (BVLS) has proven to be a viable solution approach for various applications ranging from occupancy estimation to gesture recognition. When solely capturing reflections, the scope of applications of such systems can be significantly expanded through utilizing distinct photonic materials as markers. A markers’ key requirement is that it can be distinguished from the reflections of the surroundings with unique optical properties in the intensity and/or in the spectrum of reflected light, whereas achieving generally valid unique properties is challenging. In this manuscript, we present an approach for utilizing phosphorescent markers in BVLS. Based on measuring the decay time after a light stimulus, the marker is clearly distinguishable from optical reflections of the surroundings. Importantly, a human observer recognizes neither the light stimulus nor the measuring of the decay time since both are above the perception threshold of the human eye. Our real world experiments with Ruthenium and Platinum based markers show that unique marker identification is achieved, including the differentiation between Ruthenium and Platinum markers, up to 80 cm distance between the sender/receiver and the marker. The results substantiate that phosphorescent markers in combination with BVLS have the potential for further advancements and applications.