finesse.knm.maps.Map.get_thin_lens_f

Map.get_thin_lens_f(self, double spot_size: float)

Computes the equivalent thin lens focal length from the optical path depth (OPD) in this map. Uses get_quadratic_terms().

Returns:

focal_length_x, focal_length_y

Focal length in each direction.

Notes

An ideal thin lens has an optical path length of

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

where a is the quadratic component of the OPD, and f is the focal length of the lens.