finesse.knm.maps.Map.get_radius_of_curvature_reflection

Map.get_radius_of_curvature_reflection(self, double spot_size: float)

Assuming this map’s OPD array describes a surface, this function will compute the equivalent radius of curvature from it. Uses get_quadratic_terms().

Returns:

Rcx, Rcy

Focal length in each direction, in units of meters

Notes

An ideal parabolic reflecting surface has a surface shape:

\[z = \\frac{1}{4 f} r^{2} = a r^{2} \]

where \(a\) is the quadratic component of the surface, and \(f\) is the focal length of the reflecting surface. The radius of curvature of a mirror is related to the focal length by \(2f=R\), therefore the optical path depth is

\[z = \\frac{1}{2 R} r^{2} \]