Samsung is reportedly working to put an optical fingerprint scanner on the Galaxy S8 and it will help Samsung achieve a truly full-screen device. The optical fingerprint recognition is the oldest tech, preceding the capacitive and ultrasonic solution currently used in modern devices. It is bulkier due to its need to illuminate the surface and relies on a 2D image instead of a 3D one (as is the case with Qualcomm's ultrasonic tech). Samsung may have found a way to use high-res optical sensor under its smartphone displays, and in the meantime, shrink the needed pieces to fit the Galaxy S8...
Source: http://www.gsmarena.com/samsung_galaxy_s8_may_be_the_first_to_feature_an_optical_fingerprint_sensor-news-21307.php
