EPFL Solar Energy and Building Physics Laboratory (LESO-PB)
Abstract
Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and cones, perception of light is also governed by a third class of photoreceptors, important for circadian rhythm regulation and non-visual functions such as alertness, mood and hormonal secretion. These receptors show greatest sensitivity in the blue part of the visible light spectrum. In order to assess light distribution with respect to non-visual sensitivity functions, we aimed at validating a new device to create light distribution maps with a circadian weighted radiance (Lec) which accounts for this difference in sensitivity. We utilized a camera-like light sensor (CLLS) to assess the distribution of Lec. For this purpose, we equipped the device with customized filters to adapt the camera’s spectral sensitivity to circadian sensitivity, similarly, as we had previously reported for the photometric calibration with the same device [1]. After spectral calibration and circadian weighted radiance calibration, we validated the CLLS in real scenes. The results showed that circadian luminance maps of a room can be efficiently assessed in a very short time (i.e. within 100 ms) under electric lighting as well as under daylighting conditions. We also used the CLLS to compare the Lec values between two rooms, equipped with different daylighting systems such as LightLouverTM and standard venetian blinds. Our results showed different dynamics of luminance and Lec in the course of the day with highest values at noon. We also found higher luminance and Lec values in the test room with the venetian blinds, when compared to the room equipped with LightLouversTM. Taken together, the validation of circadian luminance maps under real dynamic lighting conditions offers new possibilities to integrate the CLLS into advanced (day-) light sensors systems. This would allow to instantly adapting ambient lighting conditions with respect to tailored biological user needs
