How does the eye know when the image is in focus? There is distance measuring device, only light entering the eye. No outer feedback to be sure that focus is in fact focus not something the eye think is focus.

Question

Thank you all for your respons and upvotes.

I can now see and focus on the answer of my question 🙂

In: 3993

Answer 1

The same system that some cameras use to autofocus is used by the human eye. The focus is adjusted back and forth until the spot which has the highest contrast pixel-to-pixel (or cone-to-cone) is found.