Lichte (de)focus (named after Prof. Hannes Lichte) is the defocus setting at which the Contrast Transfer Function has the optimum contrast for electron holography (high resolution). By definition this as at a value of
Where Rmax is the desired maximum spatial frequency (corresponds to the "Up To" value set in the Quick Setup dialog, Cs is the spherical aberration coefficient of the objective lens and lambda is the wavelength of the electrons.
see for example H. Lichte, Ultramicroscopy 38, 13 (1991)