Fingerprint sensor having filtering and power conserving features and related methods
First Claim
1. A fingerprint sensor comprising:
- an array of fingerprint sensing elements;
a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element;
a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectably connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element to generate signals relating to a fingerprint; and
a plurality of switches, with each switch connected in series with a respective impedance element.
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Accused Products
Abstract
A fingerprint sensor includes an array of fingerprint sensing elements and associated active circuits and an impedance matrix filter connected to the active circuits for filtering the signals. The impedance matrix filter preferably comprises a plurality of impedance elements with a respective impedance element connectable between each the active circuit for each fingerprint sensing element and at least one other active circuit for an adjacent fingerprint sensing element. The impedance matrix filter may also include a plurality of switches with a respective switch connected in series with each impedance element. In one embodiment, the switches may be selectively operated to determine ridge flow directions of the fingerprint image. In addition, the ridge flow directions may be used to determined a core location of the fingerprint image. The switches may also be selectively operated to convert a gray scale fingerprint image to a binarized fingerprint image. Accordingly, processing of the fingerprint image may be carried out at the sensor and thereby reduce additional downstream computational requirements. In addition, sets of active circuits may be sequentially powered while the corresponding impedance elements are also sequentially connected. Further, subsets of active circuits may read during the sequential powering.
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Citations
42 Claims
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1. A fingerprint sensor comprising:
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an array of fingerprint sensing elements; a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element; a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectably connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element to generate signals relating to a fingerprint; and a plurality of switches, with each switch connected in series with a respective impedance element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A fingerprint sensor comprising:
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an array of fingerprint sensing elements; a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element; control means for sequentially powering a plurality of sets of active circuits, with each set of active circuits defined by respective fingerprint sensing elements in a corresponding predetermined area in the array of fingerprint sensing elements; reader control means for reading a plurality of active circuits in each set of active circuits as each set of active circuits is sequentially powered; a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectable connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element; a plurality of switches, with each switch connected in series with a respective impedance element. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A fingerprint sensor comprising:
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an array of fingerprint sensing elements; a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element; impedance matrix filtering means connected to said plurality of active circuits for filtering signals therefrom and comprising a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectable connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element, and a plurality of switches, with each switch connected in series with a respective impedance element; and ridge flow determining means cooperating with said impedance matrix filtering means for determining ridge flow directions in the fingerprint. - View Dependent Claims (25, 26, 27)
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28. A fingerprint sensor comprising:
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an array of fingerprint sensing elements; a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element; impedance matrix filtering means connected to said plurality of active circuits for filtering signals therefrom and comprising a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectable connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element, and a plurality of switches with a respective switch connected in series with each impedance element; and binarizing filter means cooperating with said impedance matrix filtering means for converting a gray scale fingerprint image to a binarized fingerprint image. - View Dependent Claims (29)
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30. A fingerprint sensor comprising:
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an array of fingerprint sensing elements; a plurality of active circuits with each active circuit connected to a respective fingerprint sensing element; impedance matrix filtering means connected to said plurality of active circuits for filtering signals therefrom and comprising a plurality of impedance elements connected to said active circuits so that a respective impedance element is selectable connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element, and a plurality of switches with a respective switch connected in series with each impedance element; and edge smoothing filter means cooperating with said impedance matrix filtering means for smoothing edges of a fingerprint image. - View Dependent Claims (31)
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32. A method for making a fingerprint sensor comprising the steps of:
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forming an array of fingerprint sensing elements and associated active circuits; and forming a plurality of impedance elements connected to the active circuits so that a respective impedance element is selectably connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element to generate signals relating to a fingerprint; and forming a plurality of switches with a respective switch connected in series with each impedance element. - View Dependent Claims (33, 34)
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35. A method for sensing a fingerprint using a fingerprint sensor of a type comprising an array of fingerprint sensing elements and associated active circuits, the fingerprint sensor further comprising a plurality of impedance elements connected to the active circuits so that a respective impedance element is selectable connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element, and a plurality of switches, with each switch connected in series with a respective impedance element, the method comprising the steps of:
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sequentially powering a plurality of sets of active circuits, with each set of active circuits defined by respective fingerprint sensing elements in a corresponding predetermined area in the array of fingerprint sensing elements; reading a plurality of active circuits in each set of active circuits as each set of active circuits is sequentially powered; using the switches to connect the respective impedance elements for each set of active circuits as each is sequentially powered. - View Dependent Claims (36, 37, 38)
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39. A method for sensing a fingerprint using a fingerprint sensor of a type comprising an array of fingerprint sensing elements and associated active circuits, the fingerprint sensor further comprising a plurality of impedance elements connected to the active circuits so that a respective impedance element is selectably connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for at least one other respective adjacent fingerprint sensing element, and a plurality of switches, with each switch connected in series with a respective impedance element, and an impedance matrix filter connected to the active circuits, the method comprising the steps of:
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generating fingerprint image signals from the active circuits; determining ridge flow directions in the fingerprint image signals using the impedance matrix filter by selectively operating the switches for determining signal strength vectors relating to ridge flow directions of the fingerprint image. - View Dependent Claims (40)
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41. A method for sensing a fingerprint using a fingerprint sensor of a type comprising an array of fingerprint sensing elements and associated active circuits, and an impedance matrix filter connected to the active circuits, the impedance matrix filter comprising a plurality of impedance elements with a respective impedance element connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for a respective at least one adjacent fingerprint sensing element and a plurality of switches with a respective switch connected in series with each impedance element, the method comprising the steps of:
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generating gray scale fingerprint image signals from the active circuits; converting the gray scale fingerprint image signals to binarized fingerprint image signals using the impedance matrix filter by selectively operating the switches.
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42. A method for sensing a fingerprint using a fingerprint sensor of a type comprising an array of fingerprint sensing elements and associated active circuits, and an impedance matrix filter connected to the active circuits, the impedance matrix filter comprising a plurality of impedance elements with a respective impedance element connectable between each active circuit for a respective fingerprint sensing element and at least one other active circuit for a respective at least one adjacent fingerprint sensing element and a plurality of switches with a respective switch connected in series with each impedance element, the method comprising the steps of:
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generating fingerprint image signals from the active circuits; smoothing the edges of the fingerprint image using the impedance matrix filter by selectively operating the switches.
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Specification