Indication of Mesopic Effectiveness in Light Emitting Diode (LED)-Based Lighting System

Mesopic vision plays a substantial role in energy saving, and comes into picture when we move from photopic (bright light condition, luminance > 3cd/m2) to scotopic Vision (dark light condition, luminance < 0.001 cd/m2). Mesopic vision lies in between photopic vision and scotopic vision, describing the night vision in urban areas. Here, the spectral irradiance value of white light LED and color coordinates values was theoretically calculated using McCamy formula as per CIE 1931 followed by S/P ratio (ratio of scotopic Luminaire lumens to photopic Luminaire lumens) for the different blue light component. Comparative study of the consequence of increasing blue light component has been done and resulted that S/P ratio increases with increasing the peak of blue light. In this way, LED produces more scotopic lumens than photopic lumens, and the light energy contributing in scotopic vision goes waste. Focusing on the electrical energy saving aspects of LED, a correction factor needed to be applied for getting more spectral irradiance power with minimized electrical power.