I am given the function $I_m(x,y)$ of a rendered image as well as the function $I(x,y)$ of the real image. Now I need to find the point spread function PSF. I know that
$I_m(x,y) = \iint I(x,y)PSF(x-\mu, y-\nu)d\mu d\nu$.
Does someone have a hint how to start?