Geometric distortion caused by B0 inhomogeneity is one of the most important problems for diffusion-weighted images (DWI) using single-shot, echo planar imaging (SS-EPI). In this study, large-deformation, diffeomorphic metric mapping (LDDMM) algorithm has been tested for the correction of geometric distortion in diffusion tensor images (DTI). Based on data from nine normal subjects, the amount ...

In the modern high-performance transceivers, mixers (both upand down-converters) are required to have large dynamic range in order to meet the system specifications. The lower end of the dynamic range is indicated by the noise floor which tells how small a signal may be processed while the high end is determined by the non-linearity which causes distortion, compression and saturation of the sig...

The numerical equivalent source is used to correct distortions in gravity anomalies caused by topographic relief. The error involved in the topographic correction is a function of the depth of the equivalent source. The optimum depth of the equivalent source is that which maximizes the smoothness of the calculated anomaly between control points. The technique is straightforward and can be incor...

An efficient VLSI architecture implementation for barrel distortion correction in surveillance camera images is presented. The distortion correction model is based on least squares estimation method. To reduce the computing complexity, an odd-order polynomial to approximate the back-mapping expansion polynomial is used. By algebraic transformation, the approximated polynomial becomes a monomial...

In endoscopic images, significant barrel-type distortions are introduced in case of deploying wide-angle lenses. In this work, the effect of lens distortion correction on the human experts’ classification performance is investigated. Especially, the discrimination between healthy patients and patients suffering from celiac disease is examined. Furthermore, the classification results of human ex...

The amount of information available about urban traffic from aerial video imagery is extremely high. Here we discuss the collection of such video imagery from a helicopter platform with a low-cost sensor, and the post-processing used to correct radial distortion in the data and register it. The radial distortion correction is accomplished using a Harris model. The registration is implemented in...

The paper describes solutions, how to improve a quality of basic testing methods to be possible to use them for dynamic testing high-resolution / middle speed AD converters and AD modules. The following methods are described: an application of low-distortion band pass filters, a digital correction of a known distortion of a testing signal, an application of a two-tone (or multitone) signal, an ...

OF DOCTORAL DISSERTATION HELSINKI UNIVERSITY OF TECHNOLOGY P.O. BOX 1000, FI-02015 TKK http://www.tkk.fi Author Fernando Hugo Gregorio Name of the dissertation Analysis and compensation of nonlinear power amplifiers effects in multi-antenna OFDM systems Manuscript submitted 08.06.2007 Manuscript revised 27.09.2007 Date of the defence 19.11.2007 Monograph Article dissertation (summary + original...

A new hybrid method to realise high-precision distortion determination for optical ultra-precision 3D measurement systems based on stereo cameras using active light projection is introduced. It consists of two phases: the basic distortion determination and the refinement. The refinement phase of the procedure uses a plane surface and projected fringe patterns as calibration tools to determine s...

This paper presents a pan-tilt-zoom (PTZ) camera-based displacement measurement system, specially based on the perspective distortion correction technique for the early detection of building destruction. The proposed PTZ-based vision system rotates the camera to monitor the specific targets from various distances and controls the zoom level of the lens for a constant field of view (FOV). The pr...