7,549 research outputs found
Nano-particle characterization by using Exposure Time Dependent Spectrum and scattering in the near field methods: how to get fast dynamics with low-speed CCD camera
Light scattering detection in the near field, a rapidly expanding family of
scattering techniques, has recently proved to be an appropriate procedure for
performing dynamic measurements. Here we report an innovative algorithm, based
on the evaluation of the Exposure Time Dependent Spectrum (ETDS), which makes
it possible to measure the fast dynamics of a colloidal suspension with the aid
of a simple near field scattering apparatus and a CCD camera. Our algorithm
consists in acquiring static spectra in the near field at different exposure
times, so that the measured decay times are limited only by the exposure time
of the camera and not by its frame rate. The experimental set-up is based on a
modified microscope, where the light scattered in the near field is collected
by a commercial objective, but (unlike in standard microscopes) the light
source is a He-Ne laser which increases the instrument sensitivity. The
apparatus and the algorithm have been validated by considering model systems of
standard spherical nano-particle
Fast and Accurate Algorithm for Eye Localization for Gaze Tracking in Low Resolution Images
Iris centre localization in low-resolution visible images is a challenging
problem in computer vision community due to noise, shadows, occlusions, pose
variations, eye blinks, etc. This paper proposes an efficient method for
determining iris centre in low-resolution images in the visible spectrum. Even
low-cost consumer-grade webcams can be used for gaze tracking without any
additional hardware. A two-stage algorithm is proposed for iris centre
localization. The proposed method uses geometrical characteristics of the eye.
In the first stage, a fast convolution based approach is used for obtaining the
coarse location of iris centre (IC). The IC location is further refined in the
second stage using boundary tracing and ellipse fitting. The algorithm has been
evaluated in public databases like BioID, Gi4E and is found to outperform the
state of the art methods.Comment: 12 pages, 10 figures, IET Computer Vision, 201
Fingerprint Verification Using Spectral Minutiae Representations
Most fingerprint recognition systems are based on the use of a minutiae set, which is an unordered collection of minutiae locations and orientations suffering from various deformations such as translation, rotation, and scaling. The spectral minutiae representation introduced in this paper is a novel method to represent a minutiae set as a fixed-length feature vector, which is invariant to translation, and in which rotation and scaling become translations, so that they can be easily compensated for. These characteristics enable the combination of fingerprint recognition systems with template protection schemes that require a fixed-length feature vector. This paper introduces the concept of algorithms for two representation methods: the location-based spectral minutiae representation and the orientation-based spectral minutiae representation. Both algorithms are evaluated using two correlation-based spectral minutiae matching algorithms. We present the performance of our algorithms on three fingerprint databases. We also show how the performance can be improved by using a fusion scheme and singular points
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