Solutions Work - Introduction To Fourier Optics Goodman

The quadratic phase factor inside the integral ( e^i\frack2z(\xi^2+\eta^2) \approx 1 ) when ( z \gg \frack(a^2+b^2)2 ).

Optics problems involve units (Length $L$, Length$^-1$ for spatial frequency). introduction to fourier optics goodman solutions work