Abstract— Two composite metrics to characterize display reflection, contrast, and readability under daylight illumination is proposed. A measurement of the reflection under directed illumination simulating the sun is combined with a measurement of the reflection under uniform diffuse illumination to simulate the sky. The measurements are performed separately in a laboratory, and then the measurement results are combined and scaled to daylight levels with attention to the proper spectra involved for the skylight and sunlight.

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1Reflection measurements made upon electronic displays can suffer from non-reproducibility owing to their possible strong dependence upon apparatus geometry. The geometrical dependence arises from non-Lambertian diffusion properties. We show the inadequacies of several conventional reflection measurement methods and offer some guidance on how these methods might be improved or replaced.

A newly-designed variable aperture source (VAS) characterizes specular reflection from electrophoretic e-paper displays (EPD). This 3D-printed integrating source with a capsule-shaped interior combines open-port uniformity greater than 99% with a sphereto-exit port size ratio below 1.6:1. Interchangeable aperture faceplates vary the source subtense between 1° and 17°. Reflectance vs. subtense curves demonstrated that EPD modulate specular reflection, and anti-glare surfaces reduce disturbing mirror-like reflection.