Viewing angle measurements on curved displays

Abstract

The simple fact that a curved display is no more flat induces new visual effects that must be studied specifically. Display viewing angle, generally referring to variation of emissive properties (luminance and color) versus viewing direction is generally affected by the curvature and must be measure accurately. In the following article, the angular distortion of a viewing angle measurement made on a curved display when using a standard viewing angle measurement system (goniometer or Fourier optics) is expressed versus spot size D, radius of curvature R and defocus H. The limits of validity of viewing angle measurements on a curved display are deduced. If the ratio D/R of the display is below 1%, the measurement errors in the angles cannot exceed 1° for all the viewing angles for a system at focus, and the accuracy of the measurements remains excellent. Out of focus, there is also no impact of the angular accuracy if the ratio H/R is below 1%. The simulations are compared to real measurements made across flat or bent brightness enhancement film and on a curved organic light-emitting diode cell phone display.