Non-finger object rejection for fingerprint sensors
AssigneeCypress Semiconductor Corporation
InventorsAndriy Ryshtun, Oleksandr Rohozin, Viktor Kremin, Oleg Kapshii
Life of this patent
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Abstract
A method for detecting a finger at a fingerprint sensor includes detecting a presence of an object at a fingerprint sensor and, in response to detecting the presence of the object, acquiring image data for the object based on signals from the fingerprint sensor. The method further includes, for each subset of one or more subsets of the image data, calculating a magnitude value for a spatial frequency of the subset, and identifying the object as a finger based on comparing the magnitude value to a threshold.
Claims18
A method, comprising:
- detecting a presence of an object at a fingerprint sensor;
- in response to detecting the presence of the object, acquiring image data for the object based on signals from the fingerprint sensor;
- and
- for each subset of one or more subsets of the image data,
- calculating a magnitude value for a spatial frequency of the subset,
- generating a spatial frequency spectrum for the subset by performing a discrete Fourier transform (DFT) of the subset,
- identifying a peak in the spatial frequency spectrum,
- determining the magnitude value based on a magnitude of the peak, and
- identifying the object as a finger based on comparing the magnitude value to a threshold.
A fingerprint sensing circuit, comprising:
- a hardware scan engine configured to, in response to detecting a presence of an object at a fingerprint sensor, acquire image data for the object based on signals from the fingerprint sensor;
- a finger detection module coupled with the hardware scan engine and configured to, for each subset of one or more subsets of the image data:
- calculate a magnitude value for a spatial frequency of the subset,
- generate a spatial frequency spectrum for the subset by performing a discrete Fourier transform (DFT) of the subset,
- identify a peak in the spatial frequency spectrum,
- determine the magnitude value based on a magnitude of the peak, and
- identify the object as a finger based on comparing the magnitude value to a threshold.
A fingerprint sensing system, comprising:
- a fingerprint sensor;
- a fingerprint sensor controller coupled with the fingerprint sensor and configured to:
- detect a presence of an object at a fingerprint sensor,
- in response to detecting the presence of the object, acquire image data for the object based on signals from the fingerprint sensor, and
- for each subset of one or more subsets of the image data,
- calculate a magnitude value for a spatial frequency of the subset,
- generate a spatial frequency spectrum for the subset by performing a discrete Fourier transform (DFT) of the subset,
- identify a peak in the spatial frequency spectrum,
- determine the magnitude value based on a magnitude of the peak, and
- identify the object as a finger based on comparing the magnitude value to a threshold;
- and
- a host device coupled with the fingerprint sensor.
Dependencies are inferred from the claim text.