touch ID
Touch ID is a fingerprint scanner in Apple's iPhone that is used for authentication. Touch ID is a small area on the front of the smartphone on which the finger has to be placed and which is then used to unlock the mobile device and also to make online purchases in the Apple Store. Touch ID replaces the classic authentication by password.
The fingerprint scanner of Touch ID works capacitively with a resolution of about 500 pixels per inch( ppi). Each fingerprint contains characteristic features that are manifested in arcs, swirls, branches and loops. These features are evaluated vectorially, processed via algorithms and stored in the smartphone.
The fingerprint scanner is activated when the metal ring surrounding it is touched. The captured fingerprints are compared with previously stored reference prints and if they match, the device is unlocked. Touch ID can store multiple fingers from different people as reference prints.