Fig. 1: Experimental setup of 4D-STEM.
From: Low-dose cryo-electron ptychography of proteins at sub-nanometer resolution
a A vitrified life sciences sample is illuminated with a convergent electron beam. Electrons are recorded using a pixelated detector. The convergence semi angle (CSA) is in the range of a few mrad. The beam is focused to a plane above or below sample with a defocus in the micrometer range. Figure created in Blender52, using PDB 8J5A as apoferritin model. b An example ptychographic reconstruction of apoferritin. Scale bar: 50 nm. c The sum of three 4D-STEM diffraction patterns. A typical diffraction pattern shows most of the electrons in the bright field (BF) disk of the radius corresponding to the CSA of 6.1 mrad, and some electrons are scattered to higher angles to the dark field (DF) region.
