Automated measurement of single grain orientations in the TEM

The on-line measurement of single grain orientations by the interpretation of transmission Kikuchi diffraction patterns (TKP) in the TEM is now a well-established method. Nevertheless it is time consuming and requires trained personnel. An automated technique for the interpretation of TKP has been developed. A comparison is made with similar methods for the interpretation of backscatter Kikuchi patterns (BKP) in the SEM. The pattern is recorded with a CCD camera and transferred to a computer. Kikuchi lines are detected using digital image processing. The algorithm used for the interpretation of BKP has to be modified for TKP. Special attention must be payed to the removal of the intense background and of diffraction spots which frequently appear in TKP. A Hough transform is used to reduce the problem of searching straight lines to a search for local extrema. Peaks in the Hough space corresponding to lines in the original pattern are detected after differentiation of the Hough image. Indexing of detected Kikuchi lines is performed with a modified interactive indexing program. (orig.)