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
Conventional biometric imprint devices, such as fingerprint sensors, include at least one sensor array. The sensor array includes a plurality of sensing elements usually positioned in an orthogonal arrangement of rows and columns. In these conventional sensor arrays, the size of the sensing element and the distance (pitch) between sensing elements, is determined by a required fingerprint resolution.
For example, the Federal Bureau of Investigation (FBI) requires 500 dots per inch (dpi) of resolution for fingerprint sensor arrays. Therefore, the pitch between each of the sensing elements in the sensor array must respect this 500 dpi requirement. A requirement of 500 dpi translates to 0.002 inches between each of the sensing elements. That is, if a sensor array is to meet the 500 dpi requirement, the pitch between individual sensors cannot exceed 0.002 inches.
In conventional sensor arrays that use traditional sensors, the pitch dictates the size of the sensors. That is, with all things being equal, a higher pitch will necessitate a smaller sensor. The smaller the sensor, the greater its cost due to challenges in manufacturability.
What is needed, therefore, are systems and method to increase the effective resolution of a captured biometric imprint, such a fingerprints. More specifically, what is needed are systems and methods to increase the pitch between sensing elements while, at the same time, increasing the effective resolution of the corresponding sensor array.
Consistent with the principles of the present invention, as embodied and broadly described herein, the present invention includes a method of arranging a plurality of sensor elements to form a sensor array. The method includes arranging the plurality of elements to form two or more sub-rows along an axis. Elements in a first of the two or more sub-rows are positioned in an interspersed or staggered arrangement with the elements in a second of the two or more sub-rows.
The present invention provides a unique technique for achieving a higher sensing array resolution with greater distances between sensing elements. The greater distances between sensing arrays, which can also translate into larger sensors, facilitate the construction of cheaper sensor arrays because fewer sensors will be required. Additionally, larger sensors are easier to manufacture. For example, an exemplary embodiment of the present invention enables the construction of sensing elements that are 41% larger than conventional sensors. These larger sensors, however, are still capable of meeting specified resolution requirements.
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.
More specifically, as shown in
Similarly, the distance Δ1 is also a measure of the distance between consecutive rows. The distance between consecutive rows Δ1, as is the sensor size, is also determined by the desired fingerprint image resolution but in the Y (horizontal) direction. Most fingerprint agencies, such as the FBI, require that the X and Y resolutions be the same. Therefore, the distance between consecutive rows is also Δ=0.002 inches per rows of sensing elements. The distance of 0.002 inches equates to 50.8 micro-meters (μm). As also shown in
The distance Δ1 between sensing elements in a row, and between rows limits the size of the sensing element. For example: a device having the 500 dpi requirement (in both X and Y directions) will have a sensing element that is 0.002×0.002 inches at the most (50.8×50.8 μm). In reality, most sensors are actually slightly smaller than the 50.8×50.8 μm size because manufacturing requires a non-sensing channel between these sensing elements. Ultimately, however, if a greater distance Δ between sensing elements could be achieved, while still meeting the required resolution, manufacturability could be increased and sensor array costs could be reduced.
In the exemplary embodiment of
In
Additionally, in the sensor array 300 of
More specifically, in
By the time the finger 402 has moved from one sub-row to the next, at a distance 410 of Δ1, the next frame to fill in the blanks that were lacking from the first sub-row above, are captured during a second sub-frame 403 at time T0+Δt. Ultimately, as shown below, the data captured from the first sub-row (at T0) is combined with the data captured from a second sub-row at T0+Δt to form an entire row. All of the sub-rows are then combined to form a complete frame 411. The complete frame 411 represents completed fingerprint that achieves the required resolution 412.
In the case where the sensor array height is such that multiple frames are required to reconstruct the whole fingerprint, the capture interval between sub-frames could be n*Δt. Where n is any number from 1 up to ½ the height of the sensor array. This will guarantee a minimum of 50% overlap between sub-frames. This also guarantees that all missing data from each sub-frame (grey holes) will be filled with data from the previous and/or next sub-frames. An interpolation algorithm in the time, frequency, or frequency-phase domain could be used to fill-in the missing data.
The timing difference (Δt) between the two captured sub-frames 401 and 403 is the time it takes for the finger to travel one or multiple sub-rows. This timing difference is a function of the travel speed of the finger. Thus, it is desirable that an image imprint system that embodies the sensor array 405 be able to determine the finger's swipe speed. As known in the art, finger swipe speed can be determined through a number of different techniques. The system of
More particularly,
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.