| dc.description.abstract | Along with the advancement of relevant technologies, light-emitting diode (LED) lighting has gained attention recently due to LED’s high luminous efficacy and reducing price. LED lighting is now being applied in various indoor and outdoor applications, and its development has moved forward to emphasize users’ demand and environmental protection. Watching television is like the most general leisure activity indoor; thus, user’s comfort under the display condition can be the main concern in designing indoor lighting.
This study investigates the visual comfort and visual fatigue of the user under different combinations of display luminance and contrast, which is the ratio of display luminance to background luminance. Psychophysical experiments were performed to obtain subjective ratings through questionnaires while objective ratings were acquired on visual fatigue from the critical flicker fusion and autorefractor keratometer measurements. The experiments were implemented in two rounds. ExperimentⅠhas two independent variables being the display luminance (50 nit, 100 nit, 200 nit) and the contrast (10:1, 20:1, 50:1, 217:1), where contrast 217:1 implies a darkroom condition. The levels of independent variables in ExperimentⅡare the display luminance (50 nit, 100 nit, 200 nit) and the contrast (2:1, 3:1, 4:1, 6:1, 10:1, 50:1, 217:1).
The results of ExperimentⅠshowed that the contrast is not a significant factor for the objective visual fatigue. This is probably due to the contrast levels in the experiment, and thus more contrast levels are tested in ExperimentⅡ. In the subjective assessments, there is a trend that participants felt more uncomfortable physiologically in the darkroom.
The results of ExperimentalⅡshowed that both the display luminance and the contrast are significant factors for the subjective assessments of physiological responses. Post hoc comparisons show that the display luminance of 100 nit is better than the display luminance of 200 nit and the contrast from 2:1 to 50:1 is better than the darkroom. In the subjective rating of display brightness perception, post hoc comparisons show that the display luminance of 50 nit and the contrast from 2:1 to 50:1 are preferable. In the subjective ratings of background brightness perception and environment satisfaction, post hoc comparisons show that different display luminance levels would suggest different contrast ranges.
The experimental data were used to model the ratings of display brightness perception, background brightness perception and environment satisfaction. A luminaire control model for the indoor display activities was then established based on the three fitted models with adjustable weighting factors. A higher rating from the model implies a more satisfactory lighting and display combination. The suggested luminaire operating range is defined as the region within one standard error from the highest rating of the model. | en_US |