Imaging in scanning microscopes with slit‐shaped detectors

We consider the imaging in scanning microscopes employing point and slit‐shaped detectors in both the bright‐field and fluorescent mode. In particular we consider the three‐dimensional aspects of the imaging and show inter alia that acceptable, albeit asymmetrical, images result from a slit detector system at low levels of defocus. The situation becomes worse as the defocus is increased although acceptable extended‐focus and isometric images are still possible in some cases.