The diffraction field through a finite aperture lens is obtained by using the Kirchhoff-Huygens formula. The most focused point of the diffraction field differs depending on the definition of it. The positions of the maximum axial intensity, the minimum field spread, and the maximum encircled energy are calculated and compared. They vary depending on the incidence conditions, aperture radius, and the focal length.
© 1985 Optical Society of America
Kazumasa Tanaka, Nobuhiro Saga, and Koji Hauchi, "Focusing of a Gaussian beam through a finite aperture lens," Appl. Opt. 24, 1098-1101 (1985)