In Eq. (4), we map the notation of the modified G&L OPD parameters [Eq. (2)] to the notation of the terms in Eq. (3). The specimen is comprised of $K$ stratified layers as indicated above, with each layer having RI $nsk\u200a=nl$, where ($k=1,2,\u2026,K$ and $l=3,\u2026,N$). The RIs of the immersion medium and coverglass are defined as $ni=n1$ and $ng=n2$, respectively. The thickness of the immersion medium and the coverglass are defined as $ti$ and $tg=h3\u2212h2$, respectively. The thickness of the $K$th (where the point source is located) layer is defined as $tsK=hN\u22121$, while the thickness of all the other specimen layers are defined as $tsk=hl\u22121\u2212hl$, where ($k=1,2,\u2026,K\u22121$; $l=3,4,\u2026,N\u22121$). The normalized radius ($\rho $) in the back focal plane can be used to determine the terms $cos\u2009\theta m=1\u2212sin2\u2009\theta m\u22481\u2212(\rho NA/nm)2$ for $m=1,2,\u2026,N$.