SPATIAL-DISTORTION CORRECTIONS, FOR LAUE DIFFRACTION PATTERNS RECORDED ON IMAGE PLATES, MODELED USING POLYNOMIAL FUNCTIONS

Successful integration of the spot intensities on a single-crystal X-ray diffraction image depends on the ability to predict the spot positions accurately throughout the image. In some image-plate systems, there are spatial distortions, resulting from imperfections in the scanning system, for which corrections need to be made before a satisfactory match between observed and predicted spot positions can be achieved. A procedure to correct for this spatial distortion as part of the refinement procedure used in processing Laue diffraction data is described. The spatial distortion is modelled using polynomial functions. For the test and other images considered, with a pixel size of 88 mum, the root-mean-square (r.m.s.) deviations between the observed and predicted spot positions were reduced from up to 1.4 pixels to 0.4 pixels or less for the 400 or so spots used in the refinements and good predictions throughout the images were obtained.