The PSF is introduced on page 404 in my 1979 copy of Hecht & Zajac.
Deal. Send me your book so i can bone up on optics and whatever and I’ll send you my copy of The Far Side so you can discover the joys associated with a sense of humor. My favorite is page 106. These goldfish are talking to each other outside their bowl while their castle is engulfed in flames, so....you know what? Never mind. You’ll probably suck the funny right out of the book. Sheesh. Eggheads.