Hi Haokan,

A single ray is always fully polarized (and an unpolarized ray is treated as two rays with orthogonal polarizations), so the polarization state of a single ray is always 100%, at least the way OpticStudio defines it.

To get meaningful Stokes parameters you need to trace a large number of rays and then you can compute the Stokes parameters for the average of the ensemble. This would give you parameters that represent the overall polarization state of all the rays traced. A single ray does not have a Stokes matrix, in much the same way that a single gas molecule does not have a temperature. 

• Mark

Hi @Mark.Nicholson , thank you very much for your reply. I am currently trying to use ZOS-API to chase a large number of light rays. This requires inserting the exit pupil sphere as a virtual surface, tracing a large number of light rays to the exit pupil sphere, and observing the polarized light state on the exit pupil sphere. distribution, I'm trying to program it and hope to get good results.