Hi Flo,

First of all, is the POP phase wrapped? The phase in POP is modulo-2pi, so if the phase excursion is larger than this, you'll need to unwrap the phase in something like Python or MatLab...OS doesn't have a phase unwrapping function. Remember that the POP data includes the Guoy shift, so the phase at the center is not guaranteed to be zero. 

Now when you say the 'absolute' phase, I presume you mean phase references to a plane? Phase is always referenced to something. If so, then add the spherical phase reference, which is listed in the POP analysis, to the unwrapped phase. 

- Mark

Hi Mark,

Thanks for your answer, my question was indeed about the reference phase plane. We wanted to compare the POP results with the theoretical results for a simple system. When we include the reference sperical plane radius in the POP results both results agree. 

Florence