Under-screen fingerprint reader

An optical fingerprint reader apparatus configured to detect skin features of a finger using Frustrated Total Internal Reflection contrast detection, the optical fingerprint reader apparatus comprising:

• a display comprising a transparent cover and a substrate comprising an array of active pixels, the active pixels serving as an illuminator of the optical fingerprint reader apparatus;
• a pinhole array configured to collimate reflected light rays;
• an optical sensor optically coupled to the display via the pinhole array and comprising an array of photosensors arranged on a substrate, at least the pinhole array and the array of photosensors arranged in an offset relationship with respect to one another;
• and
• a processor coupled to the display and the optical sensor, the processor configured to control illumination of selected active pixels and reading of signals from the photosensors in accordance with a predefined scanning pattern that covers a finger sensing region of the transparent cover during a fingerprint reading operation;
• wherein:
• light emitted by a selected active pixel illuminated by the processor is detected by a photosensor offset from the selected active pixel such that skin features of the finger are detectable using Frustrated Total Internal Reflection;
• the Frustrated Total Internal Reflection is dependent on a critical angle, ΘC, at an interface between a contact surface of the transparent cover and a medium external to the contact surface;
• and
• the pinhole array is arranged relative to the array of photosensors to only accept reflected rays at and higher than the critical angle, Θc.