Need to detect a crack on a lens

The image detection options offered are good for larger items. I would like to compare a small section of a lens that only differ but chip on the edges.

Would it work to just crop the smaller section from the the (large) image and work with that instead?

I cannot since the crack is induce by a short mold in our injection molding process. There area on the crack is specific and has a unique shape to it.