Comparison of fly-scanning SXDM positions in (a) externally triggered (ET) mode and (b) free-run (FR) mode, over a 2 µm × 2 µm scan subregion of a 50 µm × 50 µm scan. (c) The histogram of ET point spacing for the full scan is bimodal, while (d) the FR point-spacing histogram for the full scan is unimodal, see main text for discussion. (e) An illustration of the ET position assignment, where the heavy dashed vertical lines represent the pixel boundaries where triggers are sent to the detector, and the exposure time for each frame is indicated by the length of the arrow from the bar to the end of the arrowhead. The empty circle shows a missed frame when the trigger is issued during an exposure. (f) An illustration of the FR position assignment, where the light dashed lines represent the 20 nm encoder counts. (g) Interpolation of the positions in ET mode results in inaccurate estimation of the centre of the frames preceding a missed frame, while (h) in FR mode, the centres of all frames are accurately estimated. Note that the probe size is many times larger than the distance between stage events.