Figure 7
Image field distortion map of a test pattern imaged at cryogenic temperatures showing sub-15 nm field distortion. A Ni test pattern was imaged twice using the Ni fluorescence signal (both images had 50 nm step size and 50 ms per-pixel dwell time). The two images were then aligned by cross correlation from the center of the image, yielding an overall shift of the scan field of 2.8 pixels or 140 nm. After shifting the second image to correct for that overall shift, the image was broken up into 8 × 8 subfields. Sub-pixel-resolution cross correlation was used to measure the shift of subfields between the two images. The resulting magnitude and direction of the shift was plotted as an arrow with scaled length (scaled to 5 nm shift radius represented by the blue dashed circle). About 85% of these subfield shifts are less than 15 nm. This test shows that there is small relative distortion between images, allowing for consistent registration of images in applications such as spectromicroscopy and tomography.  [article HTML]