Direct Correlation of Ion and Electron Microscopic Images by Digital Image Superpositioning

摘要

A method has been developed whereby micrographs obtained from identical sample areas, but by different instrument and detection systems, can be correlated and superimposed upon one another through digital image processing. Various Cr-based steels were analyzed by secondary electron (SE), backscattered electron (BSE), and secondary ion microscopies, and results are presented for a sample of ordinary high-speed tool steel. Digital image superpositioning incorporates an nth-order polynomial (n < or = 3) mapping function to implement the spatial transformation and a pixel filling algorithm to estimate the corrected pixel gray level. By direct correlation of electron and ion micrographs, relative distortions caused by instrumental or operational incongruity have been removed. This methodology enables verification of secondary contrast mechanisms, such as topography, from secondary ion maps. Finally, image correlation has allowed the assessment and correlation of image distortion and astigmatism within the stigmatic ion microscope. Keywords: Secondary ion mass spectrometry; Ion microscopy; Digital image processing; Electron microscopy.