In lasers with nonorthogonal eigenmodes the excess-noise factor K can be large, especially in unstable-cavity lasers with hard-edged intracavity apertures. To the best of our knowledge, we report the first detailed study of the dependence of K on aperture shape. Calculations and measurements of K for unstable-cavity lasers with variable-size apertures of triangular, square, pentagonal, hexagona...

In this paper, we propose a method of recovering shape from shading that solves directly for the surface height using neural networks. The main motivation of this paper is to provide an answer to the open problem proposed by Zhou and Chellappa [11]. We first formulate the shape from shading problem by combining a triangular element surface model with a linearized reflectance map. Then, we use a...

A method for the extraction of the Extended Reeb Graph (ERG) from a closed 3D triangular mesh is presented. The ERG codes the relationships among critical points of the height function associated to the mesh, and it can represent isolated as well as degenerate critical points. The extraction process is based on a re-meshing strategy of the original mesh, which is forced to follow contour levels...

The presented work of this paper addresses the two shape properties, positivity and monotonicity of irregular surface data. The data is initially triangulated and a side-vertex scheme is adopted to interpolate the data over each triangle. Each boundary and radial curve is a rational function with three parameters facilitating 18 parameters in each triangular patch. The presence of these paramet...

We present in this paper a novel approach for shape description based on kernel principal component analysis (KPCA). The strength of this method resides in the similarity (rotation, translation and particularly scale) invariance of KPCA when using a family of triangular conditionally positive definite kernels. Beside this invariance, the method provides an effective way to capture non-lineariti...

In this paper, we propose to use image pixels for geometry reconstruction with a shape from silhouette approach. We aim at estimating shape and normal for the surface of a single object seen through calibrated images. From the voxel-based shape obtained with the algorithm proposed by R. Szeliski in [18], our main contribution concerns the use of image pixels together with marching cubes for con...

3D techniques are increasingly used in aerospace industry to improve quality and performance of aircrafts. This paper presents a 3D imaging technique for studying the aerodynamic shape and flight performance of micro air vehicles. 3D stereoscopic vision, based upon stroboscopic imaging, was utilized to obtain the 3D information of the aircraft’s flexible aerodynamic surface. The aircraft models...

Three-dimensional object shape is commonly represented in terms of deformations of a triangular mesh from an exemplar shape. Existing models, however, are based on a Euclidean representation of shape deformations. In contrast, we argue that shape has a manifold structure: For example, summing the shape deformations for two people does not necessarily yield a deformation corresponding to a valid...