The fresnel lens/effect is used in a number of places - Those "invisibility shields" you see videos of - In (vision) glasses, to correct for double vision (yo

The fresnel lens/effect is used in a number of places - Those "invisibility shields" you see videos of - In (vision) glasses, to correct for double vision (you can get prism in the glasses or, if the double vision is too much for that, a sticky "fresnel" lens that gets attached to the glass. I have one setting on my desk that I was using before my corrective surgery, actually... woo, tangents)