Apple latest patent integrates a fingerprint sensor in an OLED display
The US PTO published a new patent application from Apple that describes an OLED display with a built-in fingerprint reader. The idea is that integrating Near Infrared (NIR) emitters and detectors between the OLED subpixels will enable a much thinner design compared to separate display and detector layers. This also means that there is no need to have a separate reader in the home button as in current iPhones.
The Fraunhofer Institute has demonstrated bi-directional OLED microdisplays back in 2012 that are based on a similar idea - embedding photo detectors (in the visible light range, in that case) within the OLED sub pixels. The latest prototype unveiled in 2015 supports SVGA resolution and a hi-res image sensor. The bi-directional displays are available for sampling.