Definition: Aberrations which are not the primary monochromatic aberrations of spherical aberration, astigmatism, distortion, curvature of field and coma. * Also known as secondary aberrations or non-von Seidel aberrations (which are third-order).
Higher order of mathematics
Today's requirements for top-notch lenses call for computations to correct fifth-order aberrations. (The name comes from the power-series expansion of the basic Snell's Law). But designing for aspherical lenses, optical scientists have to work with seventh-order aberrations and even higher.
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