Journal of Electron Microscopy Advance Access originally published online on August 25, 2005
Journal of Electron Microscopy 2005 54(3):181-190; doi:10.1093/jmicro/dfi042
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Calibration of projector lens distortions
1 CECM-CNRS, 15 rue Georges Urbain, 94407 Vitry-sur-Seine, France, 2 Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA and 3 Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA 4 Present address: Center for Functional Nanomaterials, Brookhaven National Laboratory, Mail Stop 480, Upton, NY 11973, USA 5 Present address: CEMES-CNRS, 29 rue Jeanne Marvig, 31055 Toulouse, France
* To whom correspondence should be addressed. E-mail: hytch{at}cemes.fr
The distortions introduced into high-resolution transmission electron microscope (HRTEM) images by the projector lens system are an important source of systematic error for quantitative displacement and strain determination. Using geometric phase analysis of images of perfect crystals, we measured these errors for two different transmission electron microscopes. Local magnification varies by as much as 5%, and rotation can reach 2° across a typical image. Our experimental results are compared with theory, and optical pincushion and spiral distortion coefficients are determined. A method for calibrating and removing these distortions is presented that enables quantification to 0.1% strain and 0.1° rotation across the whole field of view. This calibration is also critical for the accurate measurement of local lattice parameters from HRTEM images.
Keywords HRTEM, projector lens, optical distortions, lattice parameter determination, strain, geometric phase
Received 28 December 2004, accepted 16 March 2005