1. Field of the Invention
The present invention relates to biometric sensing. More particularly, the present invention relates to capturing a biometric imprint using one or more sensor arrays.
2. Background Art
There are several different types of Fingerprint sensor electrical system on the market: optical, capacitive, RF, thermal, and Infra-red (amongst others). They all offer a unique combination of price, performance, reliability, and form factor. All make compromises in order to excel in select areas. None can claim to be the best in all areas.
This patent describes a new kind of fingerprint sensors based on the principle of Acoustic Impediography. A Fingerprint sensor using Acoustic Impediography is comprised of an Application Specific Integrated Circuit (ASIC or IC) and an array of mechanical oscillators used as sensing elements. It provides better price, performance, reliability, and form factor than the current state of the art fingerprint sensors.
Consistent with the principles of the present invention, as embodied and broadly described herein, the present invention includes an electrical system and method to capture a fingerprint using the principle of Acoustic Impediography. The system includes an integrated circuit and an array of mechanical oscillators used as sensing elements.
The present invention provides a unique system and method to capture fingerprints. The principle of Acoustic Impediography is used by measuring the amount of electrical current flowing through each mechanical oscillator when excited with an electrical signal at a specific frequency. When the current is measured in each sensing element, an image of the fingerprint (or portions of it) can be built using the system described in this patent.
Further embodiments, features, and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention are described in detail below with reference to accompanying drawings.
The accompanying drawings illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable one skilled in the pertinent art to make and use the invention.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.
This specification discloses one or more embodiments that incorporate the features of this invention. The embodiment(s) described, and references in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristics in connection with other embodiments whether or not explicitly described.
Each sensing element is uniquely addressable by the Integrated Circuit using transmitters and receivers inside the IC. Each row of sensing elements is connected to a single transmitter inside the IC. In addition, each column of sensing elements is connected to a single receiver inside the IC as shown in
The IC uses its integrated transmitters to generate an electrical signal that creates a mechanical oscillation of the sensing elements. This mechanical oscillation generates an acoustic wave above and below each sensing elements. Finger ridge and valleys will present different acoustic load (or impedance) on the individual sensing elements. Depending on this acoustic impedance of the finger ridge and valleys on the sensor, the acoustic wave generated by the sensing elements will be different as shown in
The ASIC has integrated transmitters connected to each row of the sensor array. Each transmitter is individually controlled by a “Transmitter Control” block. This control block determines the timing of each individual transmitter. It also controls the amplitude of the signal generated by each transmitter. It is advantageous for the transmitters to generate a sinusoidal shaped signal with a frequency matching the resonant frequency of the sensing elements. Either the series or the parallel resonance (or both) of the mechanical oscillator sensing elements could be used. A programmable “Phased Lock Loop” (PLL) is used to generate the desired frequency generated the by transmitters as shown in
The ASIC contains receivers connected to each column of the sensor array. When a single transmitter is enabled, a receiver is used to measure the amount of current flowing through a single sensing elements. Each receiver pipeline is comprised of the following elements: An input pin, A current-to-voltage converter/amplifier, A noise filter, Signal conditioning circuits, Adjustable gain and offset, and an Analog-to-Digital Converter.
Once the analog signal has been converted to a digital signal by the Analog-to-Digital Converter (ADC), it is stored into a data storage system to be processed and converted into a fingerprint image as shown in
The amount of current measured by the receiver is inversely proportional to the impedance of the individual sensing element. Which itself is proportional to the acoustic impedance of the ridge or valley on this sensing element. At the series resonant frequency the finger valley impedance is lower than the finger ridge impedance. And at the parallel resonant frequency, the finger ridge impedance is lower than the finger valley impedance as shown in
The current flowing through the sensing elements will buildup from the time the transmitter is enabled, until it reaches a steady state. This buildup time is due to the mechanical characteristics of the sensing elements. The impedance difference between ridge and valley will create different current amplitudes in the selected sensing elements as shown in
Each component in a receiver pipeline could be shared with other receiver pipelines. The ability to share components reduces the amount of circuitry inside the ASIC.
The multiplexer placement in the pipeline can vary depending on the application and performance requirements.
To improve performance sample and hold circuits can be used to break the pipeline into time slices. Different sections of the receiver pipeline can work on different sensing element data at different times.
This concept of time slicing the receiver pipeline could be modified and expended as shown in
Example embodiments of the methods, systems, and components of the present invention have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only, and are not limiting. Other embodiments are possible and are covered by the invention. Such other embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Thus, the breadth and scope of the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application claims benefit to U.S. Provisional Application No. 61/394,569, filed on Oct. 19, 2010, which is incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
61394569 | Oct 2010 | US |