Search

Automated face recognition (FR) is a well-studied problem, with a history of more than three decades. Facial recognition software that uses two dimensional (2D) images has advanced significantly in terms of accuracy over recent years. Despite the steps forward, face recognition is still not considered to be a solved problem for the cases of (i) difficult exposure conditions, such as during night-time, or in environments with unconstrained lighting, (ii) when operating at long standoff distances or at variable distances from the camera, and (iii) when using different camera sensors that operate in the same or different spectral bands. In practical forensic scenarios, it is often the case that investigators need to operate in difficult conditions, where face images captured in the aforementioned challenging cases need to be matched against good quality face images (gallery set) and where, grouping of the data in the context of demographic information (in terms of gender, ethnicity or other soft biometrics) may also be used in order to assist law enforcement officials, forensic investigators and security personnel in subject identification. In fact, in such practical scenarios, human recognition based solely on visible spectral images may not be feasible. Hence, an attractive solution is to develop efficient FR systems that can work in different practical scenarios. While different systems have been discussed and proposed over the years, an interesting approach is to increase the plurality of the source data, or in other words, start using data captured by camera sensors that cover a broad range of the electromagnetic spectrum that falls outside the visible band, including the ultraviolet (UV) and the infrared (IR) band. Thus, FR outside the visible spectrum is considered an area of growing research interest. This is further supported by the burgeoning market of camera sensors that continues to open new opportunities, at different spectral and spatial scales, in a large number of applications including those in security, forensics and defense. In light of these thoughts, the focus of this work is to expose readers to a plethora of FR advancements when operating outside the visible spectrum and our perspective on where this field is going. The discussion will include the latest studies in the UV (100–400 nm), active IR band (0.7–2.5 μ m) and, finally, the passive IR band, or more specifically, the mid-wave IR (3–5 μ m) and long-wave IR (8–14 μ m) bands. The discussion will also include research work that involves same-spectral and cross-spectral matching scenarios, where, first, face images (probes) are acquired under controlled or difficult conditions as explained above, including dealing with uncooperative subjects, and adverse environments. Then, depending on the FR scenario, the acquired probe images are matched against mug shots collected in a controlled indoor environment using a conventional camera. This paper will start by briefly covering different multi-spectral FR systems and, then, discussing various related topics (ranging from data acquisition sets, up to system performance). The paper will also suggest needed new avenues of inquiry in the context of current work in multi-spectral FR system. [ABSTRACT FROM AUTHOR]

Film over nanosphere (FON) patterns are formed by depositing a silver film on top of a close-packed polystyrene (PS) sphere template. Multiple localized surface plasmon resonance (LSPR) peaks are experimentally measured in the three-dimensional FON pattern for thin silver films. Increasing the sphere size in the close-packed template or the deposited silver film thickness red shifts the LSPR peaks to varying degrees. A finite difference time domain analysis reveals that the main LSPR peaks originate from a quadrupole and a dipole coupling mode near the triangle gap surrounded by three adjacent PS spheres. The physical location and the electromagnetic enhancement of the two resonant modes are determined for different thicknesses of deposited silver films. [ABSTRACT FROM AUTHOR]

Abstract: The use of Hydrogen Silsesquioxane (HSQ) as a negative-tone electron-beam resist and a hard etching mask to directly fabricate two-dimensional Si-based photonic crystals (PhC) was investigated. We demonstrate a protocol using the HSQ resist, including spin coating processes, low-energy electron-beam exposures, development, post-development treatments, and dry-etching, to achieve sub-micron two-dimensional photonic crystal structures in silicon. An electron-beam area dose of 315μC/cm2 at 30kV was sufficient to produce anisotropic 267-nm deep HSQ-based PhC features upon development. Subsequent oxygen plasma treatment and dry etching processes were done to transfer the final patterns to the underlying silicon with a 1:1.23 etch selectivity (Si:HSQ) using a CF4/O2 plasma. These results demonstrate the use of HSQ to simplify the fabrication processes for photonic crystals and their integration with other optical-based on-chip components. [Copyright &y& Elsevier]

The article focuses on the use of time-series detection of perspiration as a liveness test in fingerprint scanners. Fingerprint scanners may be susceptible to spoofing using artificial materials or in dismembered fingers. An anti-spoofing method based on liveness detection has been developed for use in fingerprint scanners. The method quantifies a specific temporal perspiration pattern present in fingerprints acquired from live claimants.

We report electrically controlled interfacial spin polarization, or the magnetoelectric effect in multiferroic tunnel junctions by employing organic ferroelectric copolymers, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)), as a tunneling barrier. First, we show that the ferroelectric domains and spontaneous ferroelectric polarization of the P(VDF-TrFE) films can be formed in a thin interlayer. Next, we demonstrate that the tunneling magnetoresistance in the unpolarized multiferroic tunnel junction severely quenches from 21% at 20K to 0.7% at 296 K. Remarkably, we find that the interfacial spin polarization of the device, dubbed spinterface, can be gradually tuned by controlling the ferroelectric polarization with an applied electric field. Specifically, the tunneling electromagnetoresistance can reach around 1000% while the tunneling electroresistance reaches about 30% at 200 K. We speculate that the interface might act as a polarization-dependent spin filter causing the large spinterface effect. The result suggests that organic magnetoelectric-based information storage with four-state bits is feasible at room temperature. [ABSTRACT FROM AUTHOR]

The popularity of the iris biometric has grown considerably over the past two to three years. Most research has been focused on the development of new iris processing and recognition algorithms for frontal view iris images. However, a few challenging directions in iris research have been identified, including processing of a nonideal iris and iris at a distance. In this paper, we describe two nonideal iris recognition systems and analyze their performance. The word "nonideal" is used in the sense of compensating for off-angle occluded iris images. The system is designed to process nonideal iris images in two steps: 1) compensation for off-angle gaze direction and 2) processing and encoding of the rotated iris image. Two approaches are presented to account for angular variations in the iris images. In the first approach, we use Daugman's integrodifferential operator as an objective function to estimate the gaze direction. After the angle is estimated, the off-angle iris image undergoes geometric transformations involving the estimated angle and is further processed as if it were a frontal view image. The encoding technique developed for a frontal image is based on the application of the global independent component analysis. The second approach uses an angular deformation calibration model. The angular deformations are modeled, and calibration parameters are calculated. The proposed method consists of a closed-form solution, followed by an iterative optimization procedure. The images are projected on the plane closest to the base calibrated plane. Biorthogonal wavelets are used for encoding to perform iris recognition. We use a special dataset of the off-angle iris images to quantify the performance of the designed systems. A series of receiver operating characteristics demonstrate various effects on the performance of the nonideal-iris-based recognition system. [ABSTRACT FROM AUTHOR]

Hyperfine interaction (HFI), originating from the coupling between spins of charge carriers and nuclei, has been demonstrated to strongly influence the spin dynamics of localized charges in organic semiconductors. Nevertheless, the role of charge localization on the HFI strength in organic thin films has not yet been experimentally investigated. In this study, the statistical relation hypothesis that the effective HFI of holes in regioregular poly(3-hexylthiophene) (P3HT) is proportional to 1/N0.5 has been examined, where N is the number of the random nuclear spins within the envelope of the hole wave function. First, by studying magnetoconductance in hole-only devices made by isotope-labeled P3HT we verify that HFI is indeed the dominant spin interaction in P3HT. Second, assuming that holes delocalize fully over the P3HT polycrystalline domain, the strength of HFI is experimentally demonstrated to be proportional to 1/N0.52 in excellent agreement with the statistical relation. Third, the HFI of electrons in P3HT is about 3 times stronger than that of holes due to the stronger localization of the electrons. Finally, the effective HFI in organic light emitting diodes is found to be a superposition of effective electron and hole HFI. Such a statistical relation may be generally applied to other semiconducting polymers. This Letter may provide great benefits for organic optoelectronics, chemical reaction kinetics, and magnetoreception in biology. [ABSTRACT FROM AUTHOR]