The quarter wave plate can be positioned such that the direction of {HEAD ~ the slow axis} of the quarter wave plate and {TAIL ~ the S polarization direction} are generally parallel 
of
The quarter wave plate can be positioned such that the direction of { HEAD ~ the slow axis } of the quarter wave plate and { TAIL ~ the S polarization direction } are generally parallel
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH