Adaptation luminance in a road lighting environment: analysis of non-uniform luminance distribution

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto. fi Author Mikko Maksimainen Name of the doctoral dissertation Adaptation luminance in a road lighting environment: analysis of non-uniform luminance distribution Publisher School of Electrical Engineering Unit Department of Electrical Engineering and Automation Series Aalto University publication series DOCTORAL DISSERTATIONS 172/2016 Field of research Illumination Manuscript submitted 19 May 2016 Date of the defence 25 October 2016 Permission to publish granted (date) 16 August 2016 Language English Monograph Article dissertation Essay dissertation Abstract 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 nonuniform 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.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 nonuniform 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. 1