Luca Marinozzi got his Master Degree in Physics in 2011 at University of Milan with a work on particle sizing. After that he won a grant at University of Milan working in a spin off and collaborating to build an optical-base biosensor. In 2012 he started to work in a Japanese Photomask company as Laser Writing Engineer for three years. From 2016 on he is working in Cariboni Fivep as optics developer and light engineering area coordinator.
Impact of Spectrum and Color Temperature on Circadian Clock and Melatonin Suppression – Spectra Model and Installed Projects
In order to evaluate the impact of white LED sources on circadian clock we started our work considering the model by Rea et al. and the simplified model proposed by Bellia and Seraceni.
As light sources, we considered a continuum spectrum distribution both from white phosphor converted LED for general lighting purpose available in the market and applying a suitable computational model, calculating, for each used source, the color temperature correlated to the Planckian curve (CCT), the chromatic coordinates, the color rendering index (CRI), the dominant wavelength and GAMUT AREA INDEX (GAI).
Starting from market available general lighting LED, as first step we calculated the CLA (Circadian Effects of Light) accordingly with the model defined by Rea et al. and the simplified one by Bellia and Seraceni. We used the following approach: first we considered LED sources having different color temperature within the same technology platform; then we considered LED with different technology platform and different spectral distribution but with the same nominal correlated color temperature.
As second step of our research, in order to enlarge the dataset to be analyzed, we performed the same calculation using a large number of numerical generated spectra.
Trying to validate the hypothesis of CCT as the only one good estimator for circadian light impact, we compared the results of our measurements and calculations with those obtained by our references and reported only as a function of CCT. Starting from our results, we investigated the presence of strong correlations that enable us to consider a more suitable set of parameters as good estimator for CLA.
After the validation of this approach, we took into account some installed projects. Based on regulation requirements we calculated the lux level that reach the eye of the observer in different urban settings: a M-class road model, a cycle-pedestrian path and a park installation. For each setting we considered different photometric distributions, fluxes, CCT and spectrum applying the previous model to obtain the map of circadian light and melatonin suppression for each installation.