1. A method of behind-the-lens dark-field imaging using a scanning electron microscope apparatus, the method comprising: focusing an incident electron beam onto a specimen surface using an immersion objective lens; deflecting the incident electron beam so as to scan the incident electron beam over a field of view of the specimen surface; detecting a secondary electron beam using a segmented detector to obtain a set of pixel data for each segment of the detector; compensating for scan-dependent movement of the secondary electron beam over the segmented detector by processing using a dynamic centering algorithm to generate a set of virtual pixel data for each segment of a virtual detector; and using at least one set of the virtual pixel data to generate a dark field image.