Capacitive fingerprint sensor with adjustable gain
May 13, 2017. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3781855 Capacitive touch entry apparatus having high degree of personal safety Facsimile method and apparatus for setting white level Capacitive fingerprint sensor Offset and gain correction system for image data processing Individual identification recognition system Fingerprint sensing device and recognition system having predetermined electrode activation Object position and proximity detector Apparatus and methods for measuring and detecting variations in the value of a capacitor Driver circuit for a contact imaging array InventorsAssigneeApplicationNo. 855230 filed on 05/13/1997US Classes:382/124, Using a fingerprint382/108Surface texture or roughness measuringExaminersPrimary: Boudreau, Leo H.Assistant: Werner, Frank E. Attorney, Agent or FirmInternational ClassesG06K 009/28G06K 009/36 AbstractThe present invention relates to a fingerprint sensing device comprising a planar array of closely-spaced capacitive sense elements. When a finger is placed in close proximity to the sensing device, the capacitive sense elements measure a capacitance between the finger and a single capacitor plate in each sense element. This is accomplished by precharging each capacitor plate, and then using a known current source to remove a fixed amount of charge from each capacitor plate. The measured capacitance varies as a function of the distance between the capacitor plate and the finger surface. Thus, a capacitance measurement allows the distance between the capacitor plate and the finger surface to be determined. Distance measurements across the array of sense elements are combined to produce a representation of the pattern of ridges on the finger surface which comprise a fingerprint. After a fingerprint is acquired, the quality of the fingerprint is evaluated, and if necessary, a gain parameter for the sense elements is iteratively adjusted until a satisfactory fingerprint is acquired.Other References
Field of SearchPersonnel identification (e.g., biometrics)Using a fingerprint Extracting minutia such as ridge endings and bifurcations With a guiding mechanism for positioning finger With a prism IMAGE SENSING Surface texture or roughness measuring CAPACITOR CHARGING OR DISCHARGING Junction gate region free of direct electrical connection (e.g., floating junction gate memory cell structure) Imaging array Photodiodes accessed by FETs Photoresistors accessed by FETs, or photodetectors separate from FET chip Insulated gate capacitor or insulated gate transistor combined with capacitor (e.g., dynamic memory cell) Capacitor for signal storage in combination with non-volatile storage means Capacitor coupled to, or forms gate of, insulated gate field effect transistor (e.g., non-destructive readout dynamic memory cell structure) Variable threshold (e.g., floating gate memory device) In combination with capacitor element (e.g., DRAM) In array having structure for use as imager or display, or with transparent electrode Signal voltage or gain control Shade correction Facsimile measuring, testing, or calibrating | |
