Question
I am debugging my model and ran into some questions about the orientation of polarization. Please explain the relationship between the Stokes Vector and the Global Coordinate System of the model.
Synopsis
Relationship between Stokes Vector and Global Coordinates
Solution
The Stokes Vectors reported in the Ray History (S0 thru S3) define the polarization state relative to a set of "local" coordinates. The local Z-axis coincides with the direction of propagation of the ray, and a local X-Axis (Sx, Sy, Sz) which can be thought of as an extension to the Stokes Vector is also derived. These local coordinates are not displayed in the Ray History. The combination of the Stokes Vectors and the local coordinates determine the "global" orientation of the Polarization Ellipse, and this orientation is displayed in the Ray History (Xvec MajAxis, Yvec MajAxis, Zvec MajAxis). The 3 sets of data below all represent the same "Global" Polarization State: (S0, S1, S2, S3); (Sx, Sy, Sz) >> (Xvec MajAxis, Yvec MajAxis, Zvec MajAxis) Case A = (1, 1, 0, 0); (1, 0, 0) >> (1, 0, 0) Case B = (1, -1, 0, 0); (0, 1, 0) >> (1, 0, 0) Case C = (1, 0, 1, 0); (1, -1, 0) >> (1, 0, 0) Case A S0 thru S3 indicate Linear Horizontal Polarization Sx, Sy, Sz indicate that the local X-Axis is equivalent to the global X-axis Xvec MajAxis, Yvec MajAxis, Zvec MajAxis indicate that the polarization is oriented along the global x-axis Case B S0 thru S3 indicate Linear Vertical Polarization Sx, Sy, Sz indicate that the local X-Axis is equivalent to the global Y-axis Xvec MajAxis, Yvec MajAxis, Zvec MajAxis indicate that the polarization is oriented along the global x-axis Case C S0 thru S3 indicate Linear 45 deg Polarization Sx, Sy, Sz indicate that the local X-Axis is equivalent to a global axis that is 45 deg in XY Xvec MajAxis, Yvec MajAxis, Zvec MajAxis indicate that the polarization is oriented along the global x-axis To analyze the orientation of the polarization in terms of the global coordinates of the model, I suggest reading the Xvec MajAxis, Yvec MajAxis, Zvec MajAxis that define the orientation of the Polarization Ellipse.
