A New Approach for Efficient Evaluation of Switchable Privacy Displays

Switchable privacy displays (SPD) become increasingly popular due to unmatched user experience for both mobile (smartphones, laptops) and stationary (monitors) devices. SPDs can electronically control the emission angle of the light coming out of the display. This is important for safety critical data such as PIN entry, sensitive data, and personal photos especially in public spaces and offices. Today’s displays provide either no protection or use louver films which are inconvenient in use. SPDs are also important for passenger information displays (PIDs) in cars. The most critical parameters for SPDs are the on-axis luminance for the user, the off-axis luminance for intended collaborators, and blocking the content for potential shoulder-surfers (spying, off-axis observers). Dedicated measurements and evaluations are complex and time-consuming for automotive PIDs. Our new approach is based on proven evaluation results and optical measurements, which must be performed for qualification purposes. The only additional measurement is the viewing angle characteristics in blocked (private) mode. Our method is highly efficient, as it involves extracting only a few, but most relevant luminance parameters towards acceptable threshold values. This project was carried out in collaboration with the Switchable Privacy Task Group of the Displayforum (www.displayforum.de). 108