Fingerprint sensor having spoof reduction features and related methods
DCFirst Claim
1. A fingerprint sensor comprising:
- an array of impedance sensing elements for generating signals related to an object positioned adjacent thereto; and
spoof reducing means for determining whether or not an impedance of the object positioned adjacent said array of impedance sensing elements corresponds to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger;
said spoof reducing means comprising a complex impedance detector for detecting a complex impedance having a phase angle in a range corresponding to a live finger.
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Abstract
A fingerprint sensor includes an array of impedance sensing elements for generating signals related to an object positioned adjacent thereto, and a spoof reducing circuit for determining whether or not an impedance of the object positioned adjacent the array of impedance sensing elements corresponds to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger. A spoofing may be indicated and/or used to block further processing. In one embodiment, the spoof reducing circuit may detect a complex impedance having a phase angle in a range of about 10 to 60 degrees corresponding to a live finger. Alternately, the spoof reducing circuit may detect an impedance having a phase angle of about 0 degrees or 90 degrees corresponding to some objects other than a live finger. The fingerprint sensor may preferably include a drive circuit for driving the array of impedance sensing elements, and a synchronous demodulator for synchronously demodulating signals from the array of impedance sensing elements. Accordingly, in one particularly advantageous embodiment of the invention, the spoof reducing circuit may operate the synchronous demodulator at least one predetermined phase rotation angle. More preferably, the spoof reducing circuit may cooperate with the synchronous demodulator for synchronously demodulating signals at first and second phase angles and generating an amplitude ratio thereof, and may also compare the amplitude ratio to a predetermined threshold.
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Citations
41 Claims
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1. A fingerprint sensor comprising:
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an array of impedance sensing elements for generating signals related to an object positioned adjacent thereto; and spoof reducing means for determining whether or not an impedance of the object positioned adjacent said array of impedance sensing elements corresponds to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger;
said spoof reducing means comprising a complex impedance detector for detecting a complex impedance having a phase angle in a range corresponding to a live finger. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A fingerprint sensor comprising:
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an array of electric field sensing electrodes for generating signals related to an object positioned adjacent thereto; drive means for driving said array of electric field sensing electrodes; synchronous demodulator means cooperating with said drive means for synchronously demodulating signals from said array of electric field sensing electrodes; and spoof reducing means cooperating with said synchronous demodulator means for determining whether or not an impedance of the object positioned adjacent said array of electric field sensing electrodes corresponds to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger, said spoof reducing means comprising a complex impedance detector for detecting a complex impedance having a phase angle in a range corresponding to a live finger. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for reducing spoofing of a fingerprint sensor of type comprising an array of impedance sensing elements, the method comprising the steps of:
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generating signals related to an object positioned adjacent the array of impedance sensing elements; and determining whether or not an impedance of the object positioned adjacent the array of impedance sensing elements corresponds to a live finger by detecting a complex impedance having a phase angle in a range corresponding to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A fingerprint sensor comprising:
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an array of impedance sensing elements for generating signals related to an object positioned adjacent thereto; and spoof reducing means for determining whether or not an impedance of the object positioned adjacent said array of impedance sensing elements corresponds to a live finger to thereby reduce spoofing of the fingerprint sensor by an object other than a live finger, said spoof reducing means comprising a detector for detecting an impedance having a phase angle of at least one of about 0 degrees and 90 degrees corresponding to some objects other than a live finger. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41)
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Specification