Dynamic focussing for recording images from tilted samples in small-spot scanning with a transmission electron microscope.
For three-dimensional electron microscopical structure research the specimen must be imaged in a tilted position. Specimen tilt is also often needed to achieve an optimal molecular packing orientation. The tilt with respect to the optical axis causes a defocus gradient alongside the imaged area and thus entails the following complications: 1) The phase-contrast transfer function fades for strong defocus; 2) the Fourier coefficients are split; and 3) the signal-to-noise ratio cannot be enhanced by simple averaging. An image procedure with small-spot scanning and simultaneous defocus compensation is proposed which helps to reduce these problems.
Zemlin
F
F
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Federal Republic of Germany.
D003461:Crystallography; D007089:Image Enhancement / Q000379:methods*; D008433:Mathematics; D008854:Microscopy, Electron