Abstract

The secondary maxima in the Airy pattern are saddle points in the focal region of systems of large Fresnel numbers. These saddle points leave the focal plane when the Fresnel number decreases, and, as a result, the secondary maxima in the Airy pattern are no longer the critical points in the focal region. Movement of these saddle points is in the off-axis region and in a direction opposite to the focal shift along the axis.

© 1991 Optical Society of America

Three-dimensional intensity distribution near the focus in systems of different Fresnel numbers

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Gaussian imaging transformation for the paraxial Debye formulation of the focal region in a low-Fresnel-number optical system

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