Three-dimensional morphometry in scanning electron microscopy: a techniquefor accurate dimensional and angular measurements of microstructures usingstereopaired digitized images and digital image analysis

A method for accurate dimensional and angular measurements of microstructur es analysed in the scanning electron microscope is described. The method co nsiders central and parallel projections and involves (a) digital image acq uisition of stereopaired images from the scanning electron microscope's pho todisplay, (b) generation of 3D-image representations, (c) setting of measu ring points in the digitized stereopaired images, (d) computation of exact space coordinates (x/y/z) from the corresponding point coordinates (x(L)/y( L); x(R)/y(R)), (e) determination of distances and angles between consecuti ve corresponding points using vector equations, and (f) transfer of compute d data into spreadsheets of the data analysis software using dynamic data e xchange with simultaneous graphical display of the frequency distribution o f variables. Measurements performed on specimens with known dimensions (grid with 10 mu m wide square meshes, polystyrene beads with 0.33 mu m diameter) and angles (synthetic crystals of K(Al,Cr)[SO4], CuSO4. 5H(2)O and NaCl) revealed a h igh accuracy in dimensional as well as angular measurements (total error 1 +/- 0.5%). In Monte Carlo experiments the overall error was found to depend strongly o n the size of the measured structure relative to the size of the measuremen t field (field width).