Image quality changes due to white-boost function on WOLED display

Abstract

White-boost, designed to increase the peak luminance of displays, is utilized in white organic light- emitting diodes displays with an additional white channel. This research investigates the perceptual changes in image quality brought about by white-boost function on a WOLED display by employing subjective image quality assessment, a robust method known for directly measuring image quality. The measurement of physical changes induced by the white-boost level revealed two factors associated with the display’s peak luminance: average picture level and the white-boost function. Furthermore, the activation of white-boost increased the luminance based on chroma, and the rate of increase contributes to its HSV-saturation value. Therefore, white-boost activation increase the luminance while maintaining the chrominance. The common keywords used to describe the display differences caused by white-boost activation were chosen as assessment keywords. Two approaches were employed to collect appropriate keywords - through online news scraping and surveys. NLP methods were applied to process the collected data, extracting suitable adjectives. A scaling experiment was then conducted in dim light conditions, where participants assessed two displays while simultaneously watching videos with or without the activation of white-boost. The experimental data were used to cluster the adjectives, employing PCA and GMM. The initial two experiments used two displays while controlling the product’s function “peak brightness” to modulate the level of white-boost. In HDR mode, video clips were measured through eight or four keywords in experiments, respectively. Results showed that white-boost enhanced image qualities of shine, glossy, blazing, realistic, and rich while decreased the image qualities of natural and comfort. Moreover, brightness-and-colorfulness and vividness showed a positive correlation with white-boost, aligning with trends observed in shine and realistic, respectively. The next four experiments used simulation model on the single display to test the image quality changes due to white-boost in various display conditions, the size of chromaticity gamut and luminance level of diffuse white. In SDR mode, which shows a wider chromaticity gamut compared to HDR mode in experimental condition, still images were assessed through vividness and preference. The results revealed that white-boost had a positive effect on image vividness regardless of the chromaticity gamut and the overall brightness of the displayed scene. Darker displayed scenes were more affected by white- boost activation, and the perceptual vividness continued to enhance until display white became six times brighter than the additive of primary colors. In the research, it is suggested to use the ratio of CIELAB color gamut volume changes referenced to the additive tristimulus value of primary colors to predict the image vividness changes with display condition including white-boost activation.