1 files changed, 33 insertions, 0 deletions
diff --git a/beam_tracing/python/fresnelReflection.py b/beam_tracing/python/fresnelReflection.py
new file mode 100644
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+++ b/beam_tracing/python/fresnelReflection.py
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+import numpy as np
+
+def fresnelReflection(n1, n2, thetaInc):
+# calculates intensity  reflection coefficient for s and p polarizations
+# for light travelling from material with index of refraction n1 to 
+# material with n2 
+# theta_i - incident angle in medium 1 with respect to normal, could be a vector
+# R       - coefficients of reflection array [Rs, Rp]
+# theta_t - transmitted/refracted angle in medium 2 with respect to normal
+
+   #if np.size(thetaInc, axis=0) != 1: 
+    #  error('thetaInc must be a vector or scalar')
+      
+   # see  http://en.wikipedia.org/wiki/Fresnel_equations
+   # refraction angle or angle of transmitted beam with respect to normal
+   sinThetaTrans = n1 / n2 * np.sin(thetaInc)
+   
+   # special cases: total internal reflection
+   if abs(sinThetaTrans) >= 1:
+      sinThetaTrans = np.copysign(1, sinThetaTrans)
+   thetaTrans = np.arcsin(sinThetaTrans) # angle of refraction
+
+
+   cosThetaTrans = np.cos(thetaTrans)
+   cosThetaInc = np.cos(thetaInc)
+
+   Rs = ((n1 * cosThetaInc - n2 * cosThetaTrans) /\
+         (n1 * cosThetaInc + n2 * cosThetaTrans)) ** 2
+   Rp = ((n1 * cosThetaTrans - n2 * cosThetaInc) /\
+         (n1 * cosThetaTrans + n2 * cosThetaInc)) ** 2
+   R = np.array([[Rs], [Rp]])
+
+   return [R, thetaTrans]
+\ No newline at end of file