Determination of the point resolution of high-resolution transmission electron microscope using the through-focus technique

From the viewpoint of evaluating the instrumental performance of high-resolution electron microscopy (HREM), the Scherzer condition was investigated using information theory. As a result, the optimum defocus amount Δf can be expressed based on (Csλ)12, and the formula Δf=1.12(Csλ)12 is obtained. Furthermore, a procedure for measuring point resolution using the through-focus technique is developed, and a new method for determining the spherical aberration coefficient using the variance of Δf is introduced in the procedure.