Accurate stereovision with single-column scanning electron microscope.

摘要

Accurate, 3D full-field measurements at the micron-level are of interest in a wide range of applications, including facilitation of mechanical experiments and accurate profiling of specimen surfaces at reduced length scales. Scanning Electron Microscope (SEM) systems are a natural platform for acquiring high magnification images for stereo reconstruction.;In this work, a methodology for performing accurate stereovision for three-dimensional metric reconstruction and deformation measurements using single column SEM imaging systems is described. In these studies, the specimen stage is rotated in order to obtain stereo views of the specimen as it undergoes mechanical or thermal loading. Simulations and preliminary experimental studies at 300x demonstrate that (a) spatially-varying image distortions can be removed from images using a non-parametric distortion model, (b) calibration can be performed using a combination of translation and rotation in a manner that is analogous to optical systems and (c) specimen rotation variability during the measurement phase can be controlled so that baseline strain errors are within the range of +/- 150 muepsilon. Baseline rigid body motion experiments using calibrated SEM views demonstrate that (a) all components of strain in the reconstructed object have a mean value near zero and a random spatial distribution with standard deviation ≈ 300 micro-strain.;For the cases of higher magnification, a series of camera projection models and their relations are discussed. In particular, a novel "weak perspective" model that bridging the perspective projection model and the parallel projection model is proposed. In the practical aspect, issues associating experiment at high magnifications are discussed.