finesse.knm.maps.Map.get_thin_lens_f

Map.get_thin_lens_f(self, double spot_size: float, *, average=False)

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

Parameters

spot_sizefloat

Circular spot size weighting for curvature removal [m]

averagebool, optional

Whether to return the average in x and y of the focal length

Returns

focal_lengthtuple|float

If average==False returns focal_length_x, focal_length_y Focal length in each direction. Otherwise a singular average of the values

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.