Fingerprint sensor
AssigneeSiemens Aktiengesellschaft
InventorDavid G. Edwards
Life of this patent
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Abstract
A fingerprint sensor for transforming the topological pattern of a finger into an electric output signal. The sensor includes an array of cells arranged beneath a contact surface for sensing the pressure and/or temperature variations existing at the surface as a result of a fingerprint pressed against it. Each cell includes a transistor set to operate at a point within its amplification range. This operating point is varied in dependence upon the pressure and/or temperature at the adjacent contact surface. A circuit is provided to measure the amount of current passing through the transistor in each cell and to derive an electrical output signal therefrom.
Claims19
A fingerprint sensor for transforming the topological pattern of a finger under investigation into an electric output signal, comprising
- (a) a contact body having a contact surface for receiving a contact pressure exercised by means of a finger and including a transducer element for transducing said topological pattern into a corresponding information pattern;
- (b) an array of sensing cells disposed adjacent said transducer element, each cell including a first transistor having a gain, within an amplification range, dependent upon the most adjacent portion of said information pattern;
- (c) means for setting the operating point of each of said first transistors within its amplification range;
- and
- (d) means for deriving said electrical output signal in dependence upon the current passing through said first transistors.
Dependencies are inferred from the claim text.