Seidel aberrations

Summary

The Seidel aberrations are the five primary monochromatic aberrations of a rotationally symmetric optical system: spherical aberration, coma, astigmatism, field curvature and distortion. They are the terms of lowest order in the expansion of the wave aberration that are not mere refocusing or tilt. They describe the first errors beyond the paraxial approximation and are the starting point of classical lens design.