Intra-class variation is fundamental to the FNMR performance of iris recognition systems. In this paper, we perform a systematic study of modeling intra-class variation for nonideal iris images captured under less-controlled environments. We present global geometric calibration techniques for compensating distortion associated with off-angle acquisition and local geometric calibration technique...

The famous London Underground map shows the Thames and named metro stations with railway tracks as straight line segments. Strictly speaking, it is not a map that aims at a metrically accurate depiction of the network, but it is rather a diagram that accentuates the topological relations of Underground stations. Henry “Harry” C. Beck produced the first sketch for the famous diagram in 1931. His...

There has been an increasing interest in the 3D imaging in the fields of entertainment, simulation, medicine, 3D visual communication, 3D tele-robotics, and 3D TV to augment the reality of presence or to provide vivid and accurate structure information. In order to provide vivid information in these and other 3D applications, efficient techniques to generate, store, and view the stereoscopic vi...

Introduction: Echo volumar imaging (EVI) is a 3D extension of echo-planar imaging (EPI) that allows data from an entire volume to be acquired following a single excitation. However, only a few studies to date have applied EVI to functional MRI (fMRI) due to its high sensitivity to field-inhomogeneity induced distortions. In this study, we extend two EPI distortion correction techniques to EVI: ...

The rate-distortion performance of wavelet-based mesh compression algorithms is usually only evaluated in a purely geometric sense, by measures such as the Root Mean Square Error and the Hausdorff distance, which do not capture the human visual perception of distortion. This lack of quantitative information about the perceptual effects of wavelet compression has prompted us to present a more co...

Introduction: In recent years, the use of magnetic resonance (MR) images in radiation treatment planning has drawn considerable attention. However, although the extent of a tumor can be determined in great detail on MR images, the geometric accuracy of these images is limited by distortions stemming from the inhomogeneity of the static background magnetic field, the nonlineari...

Geometric distortion may occur in the data acquisition phase in information systems, and it can be characterized by some geometric transformation models. Once the distorted image is approximated by a certain geometric transformation model, we can apply its inverse transformation for the geometric restoration to remove the distortion. Harmonic model is a very important one, which can cover other...

Optical imaging systems often suffer from distortion artifacts which impose important limitations on the direct interpretation of the images. It is possible to correct for these aberrations through image processing, but due to their calculation-intensive nature, the required corrections are typically performed offline. However, with image-based applications that operate interactively, real-time...

For multispectral sensory and geospatial data to be properly integrated they must be co-registered with known data which is a difficult and time consuming process. A persistent problem with new unregistered data is geometric image distortion. This paper deals with distortion due to disproportional transformation. Images can be disproportionally transformed because of a specific angle of data ac...

Due to storage conditions and material’s non-planar shape, geometric distortion of the 2-D content is widely present in scanned document images. Effective geometric restoration of these distorted document images considerably increases character recognition rate in large-scale digitisation. For large-scale digitisation of historical books, geometric restoration solutions expect to be accurate, g...