Around the turn of the century the electron optical components were coupled with computer control of the lenses and their alignment; this was the breakthrough which led to significant improvements both in resolution and the clarity of the images.
[1] In his original paper, Scherzer summarized: "Chromatic and spherical aberration are unavoidable errors of the space charge-free electron lens.
Due to the inevitability of spherical aberration, there is a practical, but not a fundamental, limit to the resolving power of the electron microscope.
[8] The benefit of the scanning transmission electron microscope (STEM) and its potentional for high-resolution imaging had been investigated by Albert Crewe.
He investigated the need for a brighter electron source in the microscope, positing that cold field emission guns would be feasible.
[14] Researchers found that by carefully designing these electrostatic elements, they could correct some of the spherical and chromatic aberrations that plagued early electron microscopes.
These early correctors were crucial in understanding the behavior of electron optics and provided a stepping stone toward more sophisticated correction techniques.
[citation needed] The design parameters and functional requirements for phase plates were thoroughly examined in the context of their application as spherical aberration correctors.
In particular, emphasis was placed on developing a programmable, electrostatic phase plate, highlighting its potential for precise control and adaptability in correcting aberrations.
Ondrej Krivanek and Niklas Dellby founded Nion in the late 1990s,[18] initially as a collaboration with IBM.
Aberration correction have yet to be significantly used in the life sciences, due to generally low atomic weight contrast in biological systems and also the increased radiation damage.