Search

Lateral comb resonators (LCRs) theoretically possess a symmetric structure; therefore, the electrostatic force is effective only along the axis of displacement and is neutralized elsewhere. This force is not a function of the distance between the stationary and the moving (shuttle) plates in the direction of the movement. However, manufacturing imperfections and fault conditions make the device operate asymmetrically and cause rotation of the shuttle structure in a lateral gap-closing direction, putting the device in an unstable region of operation (pull-in voltage limit). In this region, the rotated structure experiences an extra force which pulls the device into the region of instability beyond the pull-in voltage limits. This paper illustrates the application of variable structure controllers to correct such behavior and to compensate for the uncertainties that exist in the microsystem parameters. The controller is equipped with a self-tuning parameter estimation block and is designed to control the LCRs under both normal and fault conditions. The controller utilizes through-wafer optical monitoring to provide the position feedback signal. The controller is implemented in a real-time control board and is experimentally verified to demonstrate the effectiveness of the control method under different operating conditions. [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]

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.