Optical fingerprint scanner and method for detecting optical coherent gating liveness

A method for detecting optical coherent gating liveness through an optical fingerprint scanner comprising the following steps:

• a) placing of finger of a user on a platen surface of a first prism;
• b) illuminating from a light source to form a first optical path to capture a fingerprint of an external surface of the finger and a refracted path from finger surface ridges collected through imaging lenses;
• c) forming a finger external surface on a two-dimensional photodiode array;
• d) providing fingerprint data for an external surface of the finger through electronically processed output data of the two-dimensional photodiode array;
• e) emitting a broad wavelength band second light source which gets collimated by interfering with a collimating lens placed at distance to the broad wavelength band second light source to form a second optical path and a collimated second optical path;
• f) hindering the collimated second optical path received in step (e) by a second prism which is accompanied by a beam splitter coating placed on a non-platen surface of the first prism from where the light splits into two beams of splitted light;
• g) forming an interferometric path of the splitted light obtained in step (f) for a coherent gating image of a preselected internal surface plane of the finger, the surface image in a form of a refracted path hindered with additional lenses placed at a distance interjacent with a pinhole on a two-dimensional array detector;
• h) obtaining an image signal by the two-dimensional array detector reflecting a spatial micro profile depth or reflectance properties of the preselected internal surface plane of the finger;
• and
• i) detecting a final image of the finger from data collected through the two-dimensional photodiode array and the two-dimensional array detector.