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.