Interesting. From what I can find the pixel format is 4 polarization directions per pixel, 45 degrees apart. Even though there are 4 channels this doesn't allow to deduce the V Stokes parameter (this camera can't capture circular polarization). Technically one channel is redundant here, but I guess it can be useful for reducing error.

I wonder if an alternative pixel format, with 3 polarization directions 60 degrees apart and a circular polarization channel would be desirable for some applications.