Night-time driving takes place under changing mesopic conditions. Nowadays manufacturers already equip their concept cars with LED headlamps. While in case of tungsten halogen lamps and HID lamps manufacturers had no much choice in selecting spectral power distribution delivering best visibility and minimal glare, the spectrum of LEDs can be still trimmed within a reasonable range. Recently several groups, both in the USA and Europe addressed the question of mesopic photometry for night time driving situations, taking into consideration both reaction time of observing a coloured light and of achromatic threshold experiments. The paper reports on simultaneous visibility and glare experiments. Both contrast threshold (CT) and reaction time (RT) experiments have been conducted. The experiments were carried out at a luminance level of 0.1 cd/M2. This luminance level was achieved by a slide projector filtered by neutral density filters and by a data projector filtered by neutral density filters plus metal interference filters. Experiments were carried out with six young observers of good colour vision. During the experiment, the luminance of the targets was controlled by a computer. The task of the observer was to press a button, once she/he noticed the 'blinking' target. The DAC value of this target represented the contrast threshold for the wavelength currently shown. It is obvious that mesopic visibility and glare spectra are different. It is still necessary to perform measurements studying additivity, both for mesopic visibility based on CT and RT investigations as well as for glare spectral measurements, before one can draw a conclusion on how to combine the two sets of results. Further investigations are under way, both for determining discomfort glare at other angles of incidence and glare levels, checking how far the glare is distracting the observer, and whether discomfort observed by irradiation with several wavelength is additive or not.
Spectral dependence of visibility and glare
Spektrale Abhängigkeit von Sichtweite und Blendung
2005
7 Seiten, 2 Bilder, 12 Quellen
Aufsatz (Konferenz)
Englisch
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