With the progressive development of new headlamp light sources, from halogen to xenon (HID) and then to LED, the apparent brightness on the road surface has been improved as observed by headlamp engineers. However, very little quantita-tive analysis has been done on the effect of differences in spectral distribution of light sources with consideration of the characteristics of visual perception. In this study, comparative experiments were conducted on the apparent bright-ness of a road surface illuminated by the three types of headlamp light sources mentioned above, each having different spectral distributions, and the results were analyzed in terms of visual perception. The results indicate that the appa-rent road surface brightness differs among the light sources even at the same level of luminance. This demonstrates that the LED light source produces higher brightness efficiency than the HID and halogen light sources (meaning that the same brightness can be obtained from the LED at a lower level of luminance). Further, such perception changed with observer age. Instead of the spectral luminous efficiency, V (Lambda), used for the present photomet-ric system, a new spectral sensitivity, VK (Lambda), which takes account of the spectral sensitivity of the short-wave sensitive cones associated with photopic vision, was used for the examination, and it was found to be able to accurately explain the experimental results. This suggests that the apparent brightness of white light can be quantitatively compared and evaluated based on the effective luminance calculated using the spectral sensitivity that takes into consideration the contri-bution of the short-wave sensitive cones.
Study on the effect of light source spectrum on apparent road surface brightness
Untersuchung der Einflüsse des Spektrums von Lichtquellen auf die wahrnehmbare Helligkeit der Straßenoberfläche
2009
12 Seiten, 10 Bilder, 8 Tabellen, 3 Quellen
Aufsatz (Konferenz)
Englisch
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