A. Pillai

Fingerprint Recognition Algorithms for Partial and Full Fingerprints

An urgent need to develop accurate biometric recognition system is expressed by governmental agencies at the local, state, and federal levels, as well as by private commercial companies. Fingerprinting is the most practical and widely used biometric technique. The pattern of ridges and valleys of each fingerprint is unique. The minutiae based algorithm is widely used for fingerprint authentication. One of the significant parts of this algorithm is the classification of fingerprints which allows minimizing significantly the number of fingerprints referenced for each identification procedure. However, the minutiae algorithm has some serious drawbacks. If the core of a fingerprint is not visible, then identification cannot proceed. Yet in some cases, partial fingerprints need to be identified. We recently developed a novel contactless line scanner for recognition of fingerprint pattern that converts a three dimensional object like a finger into a two dimensional image with minimal distortion. This novel imaging technique based on a line by line scanned image required the development of a new recognition algorithm. In this study, we propose two new algorithms. The first algorithm, called the spaced frequency transformation algorithm (SFTA), is based on taking the fast Fourier transform of the images. The second algorithm, called the line scan algorithm (LSA), was developed to compare partial fingerprints and reduce the time taken to compare full fingerprints. A combination of SFTA and LSA provides a very efficient recognition technique.

Line Scanner for Biometric Applications

Fingerprints are the most common biometric measure taken, and in recent years electronic fingerprint scanning has become commonplace. Although contactless fingerprinting methods are used, it is more common that the fingerprint is taken by pressing the finger against a computer scanner. In the current study, the advantages of the contactless technique are combined with the very promising attributes of line scanning. Line scanner views each portion of the finger perpendicularly, therefore removing the projection errors of conventional flat scanning. The three dimensional image of a finger is recorded in pixel-thick lines by scanning the camera around the finger. The final image captures an uncoiled view of the finger. Emerging technology for biometric identification is based on storing the blood vessel map in the finger. We developed a system where line scanning of finger ridges in conventional light is taken as the camera goes clockwise around a finger and in the Infrared light the image of blood vessels is recorded as the camera goes back to its initial position. Line scanning also opens a new possibility in face recognition where the comparison of major anthropometric lines would help to immunize the recognition system against benign cosmetics as well as intentional efforts to defeat such systems through the use of make-up or plastic surgery.

Can contactless fingerprints be compared to existing database

The major development of fingerprint technology in the form of wet-ink fingerprinting was initiated and improved for forensic applications by Scotland Yard about 100 years ago. In recent years, new fingerprinting methods such as live scan and contactless methods were developed and continue to evolve. Now-a-days, compatibility between three fingerprinting libraries, namely wet-ink, live-scan and contactless becomes to be a critical problem. The large numbers of people travelling and crossing the borders are subjected to fingerprinting. The database of travelers is much larger than criminal one. In this environment, the need to produce speedy comparison results starts to be problematic because it is done by human operator to provide reliable judgment. From the technical standpoint, fingerprinting methods have improved rapidly to an extent where wet-ink fingerprinting has now been replaced by computer scanner generated images of finger, i.e. digital imaging, and recently developed contactless line scan. In current study, we developed certain steps which will make contactless fingerprints comparable to fingerprints in the other two libraries. The proposed steps are applicable to any contactless fingerprinting technique. The rate of success in comparing these three libraries is 82%. The somewhat low accuracy is introduced by the fact that in the contactless methods the position of the finger is free and not necessarily repeatable. To the contrary, contact based wet-ink and digital imaging do handle a finger in the same repeatable position. Therefore, improving designs of holders for examined fingers in contactless setting should improve the rate of success.

Hetero-structure p-i-n-i-p solar cell with virtual collector

The current efficiencies of the various types of solar cell devices that are commercially available and affordable are made of silicon, and peak at about 25%, when single crystal Silicon is used. More specialized hetero-structured designs have efficiencies that reach about 40%. This paper demonstrates the design and manufacturing of a novel hetero-structures solar device, where two identical p-i-n junctions positioned one above the other share the common n-layer. This n-layer operates as a common collector, thus settling a parallel connection of the two stacked solar cells. Due to its design with fewer epitaxial layers, the cost of production per unit solar cell will be lower than known tandem multi-junction cells. The device is estimated to have a higher power efficiency of about 48%.

Biometrics assisted secure network transactions

Biometric methods of authentication such as fingerprints, hand geometry, face recognition, voice, retina and iris scan are being increasingly used for security purposes. However online transactions still use traditional knowledge based, i.e., Personal Identification Number (PIN) or password for authentication. Such methods have proved ineffective over the course of time. Traditional key based authentication has been in use over the years, but not many forays have been made in to securing network transactions using biometrics. The length of the authentication key used in authentication systems is an important piece of the authentication process. In non-biometric authentication processes such as passwords or PIN numbers, depending on the length of the key, the information may be vulnerable to access by unauthorized users. Our system makes conventional key based authentication obsolete by replacing or supplementing the normal key characters with a personal identifier of the user. Without this biometric key the service is inaccessible. In this study we propose novel authentication protocol, based on use of a contactless undistorted fingerprint images to generate authentication key. The authentication process will be reinforced by randomly selected areas of a fingerprint that are used to generate keys. An additional layer of security is provided by using blood vessel map to determine a live finger is being used. We assert that usage of contactless, thus non-distorted, fingerprint as input to generate single session keys will enhance security of network transactions because of the amount of information in randomly selected segments of a fingerprint which is available to generate unique keys.

Selective p-i-n photodetector with resonant tunneling

There are different fundamental approaches to designing selective photodetectors, where the selectivity of optical spectra is produced by a filtering aperture. However, manufacturing of multilayered filters is cumbersome for epitaxial technology. In the current study, we offer a novel approach in design of selective photodetectors. A p-i-n photodetector with superlattices in top n-layer becomes transparent for photons where hν >Eng+En1, the light will be absorbed, simultaneously producing high energy (hot) electrons. The designed thickness of the structure does prevent thermal relaxation of high energy electrons by thus enhancing the selectivity of the photodetector. However the most important selectivity element is the resonant tunneling which does happen only for electrons occupying En1 energy levels as they transfer to levels Ei1aligne...

Hetero-structure p-i-n solar cell with high efficiency

Successful harvesting of solar energy is achieved by using tandem solar cells. Stacking one on the other different p-n diodes of semiconductor materials with various band gaps is widely used design. In terms of band gap engineering, cascaded device is the one when energy gap of the materials varies within the same device. The best example of cascaded structure is the cascaded lasers. Therefore, known varieties of solar cells could be unified by the name of tandem solar cells. Typical efficiency for this design is 22.3%. Growing epitaxial hetero-structures made of various semiconductor materials is another popular design. Typical efficiencies for these structures are 31.7%. In our study, we characterize the cascaded energy band profile, present IV characteristics, and demonstrate the efficiency of the novel solar cell is 52.85%. Current design of anti-reflection coating is based on using GaAs as anti-reflection layer.

Photodetector with uniform response in 620 nm to 870 nm range

In this study, p-n junction, which consists of a p-type region of In_0.4Ga_0.6P 5 mum thick layer doped to the level of N_A= 10¹⁴ cm^-3 is developed. The n-type region is doped to the level of N_D= 10¹² cm^-3 and consists of modulation doped layers ranging from In_0.4Ga_0.6P to In_0.9Ga_0.1P. And photodetector with an approximately uniform response in the near-infrared spectrum between 620 nm to 870 nm is designed.