Geometrically, the autocorrelation of a square of side $w$ is a triangle function. The area of the pupil is $w^2$. The resulting OTF in one dimension is: $$ \textOTF(f_x) = \Lambda\left(\fracf_x2f_cutoff\right) $$ Where $\Lambda(x)$ is the triangle function ($1-|x|$ for $|x|\le 1$).

Problems here involve quadratic phase factors. Look for "completing the square" opportunities within the exponents to evaluate the integrals. The Fraunhofer Limit: When

To help you work through a specific challenge, which chapter or concept are you currently stuck on?

Official and unofficial resources exist to help verify your work: introduction to Fourier optics - 百度文库