[[The]] effect of spectum on discomfort glare

Abstract

A literature review was undertaken to understand the scope of available data regarding spectra and discomfort glare. The result of this initial investigation provided the basis for the experimental design and protocol. This laboratory study investigated subject response, measured in terms of a subjective rating scale, to five nearly monochromatic light sources at three illuminance levels for subjects of varying ages. It was found that the SPD of a glare source had a statistically significant effect on discomfort glare. Further, the 450 nm glare source produced significantly more discomfort for equal illuminance at the eye than all others tested. From the analyses of the data a new sensitivity function, VDG(λ), was developed based on the data collected for monochromatic light sources. To test the applicability of the VDG(λ) to headlamps in driving applications, the function was fitted through a set of data collected for broadband, nominally white sources, resulting in a fairly high coefficient of determination (R2=0.95). Additionally, it was found that on average, the effect of age on discomfort glare did not reach significance. However, closer inspection of the data for the two different age groups tested showed a slight difference in the response to the 450 nm stimulus. The relative contribution of short wavelength energy to the annoying experience of discomfort glare is discussed. The positive impact of the results of this study to the future development of automotive forward lighting, as well as exterior lighting in general are discussed.

Developments in automotive forward lighting, specifically the introduction of new lighting technologies such as high intensity discharge (HID) and light emitting diodes (LEDs), have led to growing concerns regarding discomfort glare. Recent studies suggest that the spectral composition of the light sources used in forward lighting impacts the amount of discomfort glare they elicit. This study explored the effects of spectral power distribution (SPD) on discomfort glare to determine its action spectrum and contribute to the growing body of knowledge that could soon offer insight into the physiological mechanism behind this subjective response.