Subject: how to obtain circular polarization in oblique incidence phase retarder

An oblique incidence total internal reflection phase retarder with the entrance 
and exit faces parallel. the input angle of incidence is 60 degree. the 
refractive index of the retarder material(flint glass) is 1.7.The retarder is 
designed to introduce a retardance of 90 degree at 589 nm. If the incident 
polarized light is at azimuth 45 degree,the beam leaving the retarder will be 
elliptically polarized. At what azimuth should the polarizer be adjusted to 
obtain circularly polarized light. how this azimuth is calculated.

Re: how to obtain circular polarization in oblique incidence phase retarder