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Aberration spotter's guide

The chart below shows the appearance of various aberrations on the ray fan and OPD fan. Included is the first order "aberration" of defocus, as well as the four Seidel aberrations that are visible on these fans: spherical aberration, coma, astigmatism, and field curvature.

In each small plot, the horizontal axis is the normalized pupil coordinate P, running from -1 to +1. The vertical axis is the ray intercept deviation (for the ray fan) or OPD (for the OPD fan), in arbitrary units. The thin horizontal line indicates zero. Thick solid lines are for rays in the tangential (or meridional) plane, thick dashed lines are for rays in the sagittal plane. If there is no dashed line it means the sagittal curve is equal to the tangential one.

The OPD is the negative of the integral of the ray fan. For example, spherical aberration has a ray fan varying as -P 3, so the OPD varies as P 4.

AberrationOn axisOff axis (y > 0)
Ray fanOPDRay fanOPD
Defocus
Spherical aberration
Coma
Astigmatism
Field curvature

See also