The Effects of Illuminance Distribution on the Desk and Ceiling Reflection for the Visual Fatigue

Abstract

In this paper, the relation between illuminance distribution on the desk, veiling reflection and visual fatigue is described.The room chosen for the experiment was 2. 5 m by 3. 3 m by 2. 8 m high. A space ofthe visual task performance was illuminated by ceiling fittings and table lamps. Light sources were cool white fluoresent lamps and incandesent lamps. The illumination levels were adapted for the performance of visual tasks from 300 lx to 700 lx on the surface of the visual task chart.The visual task consisted in the recognition of small Landolt's rings of 2. 5 mm diameter printed with black ink of 3% reflectance on the mat white paper (90% reflectance) or grossy paper (90. 5% reflectance). Besides, the subject read the books as visual task. The task time was limited to 80 minutes or 120 minutes.The degree of the visual fatigue was estimated with the fluctuation rate of the accomodation time of the eye during the visual task performance.The following results are obtained:(1) Generally, the more uniform the illuminance distribution, the less the increase of the eye fatigue.(2) In order to decrease the eye fatigue by the veiling reflection, good lighting methods on the desk is to locate the ceiling fittings in the position out of specular reflected zone.(3) The eye fatigue is most remarkable under the local lighting by only the table lamp. The eyefatigue under the locallighting used together general lighting is remarkable as compared with that under the general lighting.