The application of iterative techniques to the investigation of strong phase objects in the electron microscope

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Abstract
Modifications to iterative procedures for recovering phase information from recorded electron intensity distributions, which are applicable to strong, periodic phase objects are considered. Test calculations involving functions resembling those encountered when studying magnetic thin films in the electron microscope are made, and in particular the success or otherwise in recovering the original phase function, when only imperfectly recorded electron intensities are available, is discussed. For objects with peak-to-peak phase shifts less than 10 radian considerable success is achieved, but only if some a priori knowledge of the nature of the specimen is available have satisfactory results been obtained for stronger phase modulators. Under suitable conditions rapid and accurate results may be obtained for objects with peak-to-peak phase shifts of 30 radian using an appropriate iterative technique.