pro polarization_map45, p0in,  p45in,  p90in, p_angle, p_fraction,  Iu, Ip
  p0 =  double(p0in)
  p45 =  double(p45in)
  p90 =  double(p90in)

  p_angle = atan( ((2.0D*p45) - p0 - p90)/(p0-p90) ) / 2D

  Ip =  (p0 - p90) / ( cos(p_angle)^2D - sin(p_angle)^2D )
  Iu = p0 + p90 - Ip
  p_fraction =  Ip/(p0+p90)

end