US 9,811,708 B2
Method and fingerprint sensing device with finger lost detection
David Carling, Mölndal (SE); and Hans Thörnblom, Kungsbacka (SE)
Assigned to FINGERPRINT CARDS AB, Göteborg (SE)
Filed by Fingerprint Cards AB, Göteborg (SE)
Filed on Jun. 8, 2016, as Appl. No. 15/176,622.
Claims priority of application No. 1551263 (SE), filed on Oct. 2, 2015.
Prior Publication US 2017/0098109 A1, Apr. 6, 2017
Int. Cl. G06K 9/00 (2006.01)
CPC G06K 9/0002 (2013.01) [G06K 9/001 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A fingerprint sensing device for sensing a fingerprint pattern of a finger touching a sensing surface of said fingerprint sensing device, and providing a representation of the fingerprint pattern, said fingerprint sensing device comprising:
an array of sensing elements for sensing said fingerprint pattern;
readout circuitry connected to said array of sensing elements; and
finger detecting circuitry for detecting if a finger candidate is touching the sensing surface of said fingerprint sensing device,
said fingerprint sensing device being controllable between an active state with an active state energy consumption and an inactive state with an inactive state energy consumption lower than said active state energy consumption, wherein:
when said fingerprint sensing device is in said active state, each sensing element in said array of sensing elements is controllable to provide a sensing signal indicating a local distance between said finger and said sensing element;
and said finger readout circuitry is controllable to read out said sensing signals from each of said sensing elements and provide said representation of the fingerprint pattern based on the sensing signals from said sensing elements; and
when said fingerprint sensing device is in said inactive state, said finger detecting circuitry is configured to provide a finger candidate lost signal for indicating when said finger candidate no longer touches the sensing surface of said fingerprint sensing device.