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Fingerprint sensing system configured to determine if a finger contacts a fingerprint sensor

  • US 10,325,168 B2
  • Filed: 11/09/2017
  • Issued: 06/18/2019
  • Est. Priority Date: 12/20/2016
  • Status: Active Grant
First Claim
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1. Method performed by a fingerprint sensing system of determining if a finger contacts a fingerprint sensor of the fingerprint sensing system, comprising:

  • capturing an image of an object contacting the fingerprint sensor;

    determining an intensity for a plurality of pixels of the captured image;

    computing, for each of said plurality of pixels of the captured image, a Hessian matrix where the components of the Hessian matrix consist of second-order derivatives of the pixel intensity in the captured image;

    computing the square of the Hessian matrix;

    computing a squared Fractional Anisotropy, FA, measure using eigenvalues of the computed squared Hessian matrix; and

    determining from the squared FA measure if local pixel intensity variation is dominated by a single direction, in which case the object on the fingerprint sensor is considered to constitute a finger.

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