In mesopic photometry, neither the scotopic V'(λ) nor the photopic V(λ) spectral luminous efficiency function solely applies. Instead, the spectral distribution of the luminaire and the adaptation state of the retina determine the mesopic spectral luminous efficiency function Vmes(λ). The mesopic luminance region was defined as 0.005 cdm-2 – 5 cdm-2 by CIE (Commission Internationale de l'Eclairage) in 191:2010 system for mesopic photometry. However, the system for mesopic photometry cannot be fully utilised, until we have defined how to determine the state of adaptation – the adaptation luminance. The aim of this work was to analyse the adaptation luminance in road lighting environment. Firstly, the test subjects' contrast thresholds within visual fields with non-uniform luminance distributions were examined. Secondly, the influence of disability glare sources on the adaptation luminance was quantified. Thirdly, a novel approach, where imaging luminance photometry is combined with 3D laser scanning, was examined. Luminance non-uniformity clearly hindered the visual performance. The contrast threshold required for target detection could be 100% more on a luminously non-uniform background compared to a uniform background. The results also indicated that different retinal coordinates adapt independently to a local adaptation luminance. In the street environment measurements, veiling luminance increased the adaptation luminance by 29% on average. Veiling luminance increases the adaptation luminance which shifts the spectral sensitivity in the retina towards photopic. This induced an average difference of |0.6% | in mesopic luminance calculation. The observer's longitudinal location affects the adaptation luminance and the mesopic luminance in the measurement area. The location-dependent relative standard deviation among the calculated mesopic luminance values was 4.4%. Combining luminance measurements to laser-scanned point clouds gave promising results. The method for the 3D location and luminance data integration was found successful. In the field of lighting science, numerous further studies are needed before the adaptation luminance can be determined accurately. Firstly, no veiling luminance model can yet be utilised to an arbitrary retinal coordinate. Secondly, the effect of a constantly changing visual environment should be quantified. Thirdly, the physiological adaptation and the cognitive processing should be separated in terms of visual performance. In practical road lighting measurements though, the luminance in the measurement area can be a sufficient estimation for the adaptation luminance.
|Translated title of the contribution||Adaptaatioluminanssi valaistussa tieympäristössä: epäyhtenäisen luminanssijakauman analyysi|
|Publication status||Published - 2016|
|MoE publication type||G5 Doctoral dissertation (article)|
- adaptation luminance
- mesopic photometry
- road lighting
- disability glare