I\left(x_2, y_2\right) = r_{o}^2 + \frac{1}{\lambda^{2} f^{2}} S^{2}\left(\frac{x_{2}}{\lambda f}, \frac{y_{2}}{\lambda f}\right)+\frac{2 r_{o}}{\lambda f} S\left(\frac{x_{2}}{\lambda f}, \frac{y_{2}}{\lambda f}\right) \cos \left[2 \pi \alpha y_{2}+\psi\left(\frac{x_{2}}{\lambda f}, \frac{y_{2}}{\lambda f}\right)\right] .
