In this paper, the relation between various light sources and visual fatigue is described.
The room chosen for the experiment was 2.5m by 3.3m with a ceiliing suspended at a height of 2.8m. A space of the visual task performance was illuminated uniformly by luminaires on the ceiling. Light sources were fluorescent lamps, incandescent lamps, colored fluorescent lamps, and sodium lamps. Four levels of illumination were adopted for the performance of visual tasks in a series of 50lx, 100lx, 300lx and 600lx on the surface of the visual task chart.
The visual task consisted in the recognition of small Landolt's rings of 2.5mm diameter printed with black ink of 3% reflectance on white or gray paper, the reflectance of which was about 90%, 60%, 20% and 12%.The task time was limited to 60 minutes or 80minutes. The degree of the visual fatigue was estimated with the fluctuation rate of the accommodation time of the eye during the visual tak performance.
The following results are obtained:
(1) The eye fatigue is more remarkable under the sodium ilamp lighting than under the fluorescent lamp.
(2) The eye fatigue under the sodium lamp lighting is remarkable as compared with that under the colored fluorescent lamp lighting.Remarkable eye fatigue seems to result from the narrow wevelength band of the spectral distribution of colored soures.
(3) Using the visual task chart with black rings on white backgrowned, generally the higher the color temperature of the lampt used, the lager the increase of the eye fatigue.
(4) In the range of illumination levels from 50 to 600lx in this experiment, the eye fatigue decreased with the increase of illumination levels.
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