def _reflectance(
power_in, power_out, theta_in, theta_out, index_in, index_out):
"""Return reflectence corrected for refraction into and out off the mirror
substrate.
"""
trans_in = fresnel_coefficients(theta_in, index_out, index_in)['T']
trans_out = fresnel_coefficients(theta_out, index_in, index_out)['T']
return power_out / (power_in * trans_in * trans_out)
def _fresnel_correction(theta_in, index_lab, index_optic, **kwargs):
"""Return the Fresnel loss correction factor T_in * T_out for
a beam passing through a plate optic with refractive index index_optic
from an environment with index index_lab at an incidence angle theta_in
radians."""
theta_in_error = kwargs.pop('theta_error', 0.003)
fresnel_in = fresnel_coefficients(
theta_in,
index_lab, index_optic)['T']
fresnel_out = fresnel_coefficients(
snells_law(index_lab, index_optic, theta_in),
index_optic, index_lab)['T']
fresnel_correction = fresnel_in * fresnel_out
fresnel_correction_error = fresnel_correction - (
fresnel_coefficients(
theta_in + theta_in_error,
index_lab, index_optic)['T'] *
fresnel_coefficients(
snells_law(index_lab, index_optic, theta_in + theta_in_error),
index_lab, index_optic)['T'])
return (fresnel_correction, fresnel_correction_error)
