Computing the phase distribution $\phi (x,y)$ requires at least three interferograms. Existing literature^{6} has shown that increasing the number of interferograms can appropriately improve the accuracy of surface topography measurements. A five-step algorithm is given as Display Formula
$I1(x,y)=I0(x,y)+I0(x,y)\xb7A\u2009cos[\phi (x,y)+\psi 1],$(5)
Display Formula$I2(x,y)=I0(x,y)+I0(x,y)\xb7A\u2009cos[\phi (x,y)+\psi 2],$(6)
Display Formula$I3(x,y)=I0(x,y)+I0(x,y)\xb7A\u2009cos[\phi (x,y)+\psi 3],$(7)
Display Formula$I4(x,y)=I0(x,y)+I0(x,y)\xb7Acos[\phi (x,y)+\psi 4],$(8)
Display Formula$I5(x,y)=I0(x,y)+I0(x,y)\xb7A\u2009cos[\phi (x,y)+\psi 5],$(9)
where $\phi (x,y)$ is the phase to be determined, and $\psi 1$, $\psi 2$, $\psi 3$, $\psi 4$, and $\psi 5$ are the initial phase values of the five interferograms, respectively.