Showing papers on "Contrast transfer function published in 1968"

The relation between the spherical aberration and distortion coefficients of electron probe-forming and projector lenses

Abstract: The asymptotic spherical aberration and distortion coefficients of electron lenses always depend upon the position of the object, or the magnification, in a very simple way, and furthermore the quantities that specify the distortion are closely related to those giving the spherical aberration. These relationships are set out, and numerical values of the coefficients concerned are tabulated for Glaser's bell-shaped model; both the symmetric and the asymmetric bell are considered, and the effect of scaling with respect to the minimum projector focal length is investigated.

Eliminating Spherical Aberration and preserving Phase Contrast Information in Electron Microscopy

Abstract: THE method proposed here enables, in principle, the optical system of a conventional electron microscope to be used to determine both amplitude and phase, free from spherical aberration, of the electron wave transmitted through a two or three dimensional crystallite of sufficiently large unit cell. The condition that the specimen must be a crystallite is probably unavoidable in any method of high-resolution electron microscopy, because the severe electron radiation damage of organic substances will probably prevent the visualization of isolated molecules at atomic resolution. The further condition, that the two shortest unit cell dimensions of the crystallite should be more than about 10 A (using a good conventional electron microscope), is satisfied by most substances of biological interest.