Lighting for projector use in school classrooms to improve visibility

Projectors have become very popular in school classrooms in China. However traditional lighting design does not consider lighting influence on the visibility of projection screen. The aim of this study was to investigate the current lighting conditions in classrooms when watching a projection screen, and then to search for lighting conditions providing better visibility. A survey was carried out to collect desk illuminance, projection screen luminance and contrast from eight schools in four cities in China. Based on the survey, an experiment was designed and performed with three ambient illumination conditions (i.e., 0lux, 300lux, daylight), five different projection screen luminance levels (i.e., 50, 100, 150, 200, 260 cd/m²), and five seating positions. The results indicate that the ambient illumination, the projection screen luminance, and the seating position all have a significant influence on the visibility of gratings on the projection.