Wave Theory of Image Formation and Resolution
Bethe A. Scalettar, James R. Abney, Cyan Cowap · 2022
This chapter deals with one key measure of image quality: resolution. Resolution refers to the ability to discriminate closely spaced objects. The chapter begins with a discussion of wave optics, particularly the superposition phenomenon known as diffraction, which plays a key role in dictating resolution. This is followed by a discussion of tools that are used to quantify resolution, notably transfer functions and smallest resolvable spacings. The chapter concludes with a discussion of the Rayleigh and Abbe theories of diffraction-limited resolution. Both theories similarly conclude that resolution improves with decreasing radiation wavelength and increasing lens numerical aperture (light gathering ability). The Abbe theory is given more extensive treatment because it is more rigorous, provides insight into key methods of image enhancement, notably spatial filtering, and is closely linked to the modern theory of Fourier optics.