Köhler illumination and brightness measurement with lanthanum hexaboride cathodes Available to Purchase

An aperture illumination system such as a Köhler system offers the ability to illuminate an electron probe system with the peak brightness from an electron source. It also provides an object with an ideal step‐function current distribution. This paper describes results obtained using Köhler illumination on a short focal length final lens SEM. Application of the SEM to brightness measurement is discussed at some length. Examples of overall probe performance for scanning transmission electron microscopy, low‐loss surface microscopy, and microfabrication are also given.