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Ultrasonic fingerprint authentication based on beam forming

  • US 9,424,456 B1
  • Filed: 06/24/2015
  • Issued: 08/23/2016
  • Est. Priority Date: 06/24/2015
  • Status: Expired due to Fees
First Claim
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1. A method of generating a three-dimensional representation of a fingerprint using ultrasound, the method comprising:

  • scanning, by a device, a first region of a fingertip with a first directed series of ultrasonic pulses to determine a first location in a first dimension and a second dimension of a first ridge of a plurality of ridges, the ultrasonic pulses of the first directed series having a first ultrasonic frequency;

    scanning, by the device, a second region of the fingertip with second directed series of ultrasonic pulses to determine a second location in the first dimension and the second dimension of a second ridge of the plurality of ridges, the ultrasonic pulses of the second directed series having a second ultrasonic frequency that is different from the first ultrasonic frequency, wherein the scanning of the first region overlaps in time with the scanning of the second region;

    emitting, by the device, diffuse ultrasound at a third ultrasonic frequency having a first wavelength toward the fingertip;

    determining, by the device, a third location in the first dimension and the second dimension where a first peak magnitude of first reflections occurs at a fourth ultrasonic frequency corresponding to a second wavelength, wherein the second wavelength is equal to the first wavelength or a harmonic of the first wavelength;

    determining that a first depth in a third dimension of a first valley at the third location is equal to the second wavelength;

    emitting, by the device, diffuse ultrasound at a fifth ultrasonic frequency having a third wavelength toward the fingertip;

    determining, by the device, a fourth location in the first dimension and the second dimension where a second peak magnitude of second reflections occurs at a sixth ultrasonic frequency corresponding to a fourth wavelength, wherein the fourth wavelength is equal to the third wavelength or a harmonic of the third wavelength; and

    determining that a second depth in the third dimension of a second valley at the fourth location is equal to the fourth wavelength;

    combining the first location of the first ridge and the second location of the second ridge to generate a two-dimensional representation of locations of the plurality of ridges of the fingerprint; and

    overlaying the two-dimensional representation of the locations of the plurality of ridges on the first depth of the first valley at the third location and the second depth of the second valley at the fourth location to generate the three-dimensional representation of the fingerprint.

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