ABSTRACT
In electron and ion probe-forming systems, the spatial resolution is usually the most important characteristic of the optical system. This chapter presents how the information passing capacity is applied to the determination of resolution, and how it is calculated exactly or approximated in practical applications for both electron and ion beam systems. There are two important approaches which are widely used to determine the resolution of an optical system. One is to define it by the beam size, and the other is to define it from the spatial frequency response of an optical system calculated from the Fourier transform of the beam intensity distribution. Rayleigh’s criterion can be applied to the definition of resolution and generalized by using the intensity distribution of a beam instead of the Airy pattern. Rayleigh’s criterion is determined from contrast in the image for neighboring point like objects.
