Field studies on the duration of fixation during driving reveal that in daytime the fixation rests on average about 0.2 seconds on a point in the field of view. Thus, the time available to read traffic signs is limited. In order to obtain quantitative data, the visual acuity and its dependency on the observation time had been investigated in two independent studies. Landolt-Rings in negative contrast were presented on a computer-screen of 10 - 40 cd/sq.m Luminance as a background. The display of the rings could be varied between 2 and 0.02 seconds and shown in different contrasts. It became evident that the visual acuity depends on the log of the light dose reduced by the transmission in the eye media, so that absorbed photons seem to determine visual resolution. For young observers it was found that visual acuity decreases with shorter observation time and lower contrast that can be described by an algorithm for calculation. For the covering abstract see ITRD E123380.
Abstract