d:x reflectance measurement for curved surface with integrating sphere

Abstract Ambient contrast ratio (ACR) is a useful parameter to evaluate the quality of displays when used under diffuse lighting conditions. The methodology recommended by most documentary standards calculates the ACR of the display from d:x reflectance. Reflectance measurement of flat surfaces typically employs an integrating sphere and a flat white reference plate. However, the shape difference between the flat white standard and test curved sample causes changes to the amount of light illuminating their surfaces and thus gives measurement errors. Especially for concave test surfaces, the error is significant when the sample has small radius of curvature. To increase the measurement accuracy, this paper derives the correction factor to compensate the effect caused by shape difference between the reference plate and test curved sample. The associated uncertainty analysis is also discussed in this paper.