Halo Measurements: OLEDs vs. FALD LCDs

Modern displays must have a high contrast ratio resulting in deep black. However, bright white content spreads into surrounding dark areas (this effect is called halo or Mura Hamo) thus reducing the local contrast ratio. We report on a new measurement method for comparing the impact on OLEDs and FLAD (local dimming) LCDs. The results show that the halo luminance spreads over 10 mm and more with exponential decay. The relative halo luminance is about 5x larger for a high end LCD compared to an OLED. Evaluations with subjects show that halo is significantly less noticed for positive contrast compared to negative contrast (being typical for automotive GUIs).