Practical Electron Microscopy and Database

In TEM operations, diffraction focus is performed with “Diff focus” knob. In this action, the focus of the first intermediate is adjusted at the back focal plane of the objective lens (see page1985).

To have a camera length exactly as labeled in the instrument, some key points need to be satisfied as follows:
         i) The specimen should be placed exactly at the Eucentric height in the objective lens.
         ii) A parallel electron beam should be employed.
         iii) The focus of the objective lens should be exactly adjusted to the focus position.
         iv) The focus of the first intermediate (with “Diff focus” knob) should be adjusted at the back focal plane of the objective lens.