Fingerprint sensor with liveness detection

A fingerprint area sensor device with built-in liveness detection capabilities, comprising:

• an area sensor disposed on a top surface of a substrate, wherein the area sensor includes an integrated pressure or proximity sensor;
• a stiffener disposed below a bottom surface of the substrate;
• a flexible printed circuit making electrical connection to the sensor, the flexible printed circuit extending from the top surface of the substrate to a bottom side of the stiffener;
• a light source and a photodetector disposed on the flexible printed circuit;
• wherein the stiffener includes a first through-hole located with respect to the light source to allow light from the light source to transmit through the stiffener towards a finger located on the area sensor,
• wherein the stiffener includes a second through-hole located with respect to the photodetector to allow light reflected from the finger to pass through the stiffener to the photodetector;
• and
• a microcontroller disposed on the flexible printed circuit and configured to obtain reflected light data upon detection of a finger on the area sensor through the integrated pressure or proximity sensor for use in liveness detection analysis.

A method comprising the steps of:

• detecting presence of a finger on a fingerprint area sensor using a first detection threshold;
• upon detecting the presence of the finger using the first detection threshold, perform liveness detection measurements using a light source and a photodetector disposed below a sensing area of the fingerprint area sensor;
• detecting presence of the finger on the fingerprint area sensor using a second detection threshold greater than the first detection threshold;
• and
• upon detecting the presence of the finger using the second detection threshold, perform a fingerprint scan of the finger.