Surface-specific lighting scenarios enhancing the perceptibility of 3-dimensional flaws

Abstract

In order to rate the ergonomic quality of lighting scenarios with respect to the use of directional and diffuse lighting in laboratory studies, Landolt rings (test signs) were carved into typical industrially manufactured surfaces via laser, representing three-dimensional "reliefs." Besides illumination with a luminance level of 750 lx (lighting scenario 1), which is recommended for inspection tasks according to a European standard, diffuse light (lighting scenario 2), directional light (lighting scenario 3), and lighting which was specifically chosen for each of the five surface types (lighting scenarios 4–8 were utilized. The general result of the analysis of the objective data showed that three-dimensional reliefs on typical industrially manufactured surfaces are usually easier to recognize under directional light (lighting scenario 3) than under diffuse light (lighting scenario 2). At the same time, however, the test subjects indicated on the questionnaires that illumination with pure directional light was often perceived as uncomfortable. Illuminations which combined directional and diffuse light were usually a good compromise between the objective results and the subjective evaluations and can generally be recommended for mainly diffuse reflecting surfaces.