That compactness is what [WalkerDev] found attractive, and in the process discovered that stacking two different Fresnel lenses and putting them in a 3D printed housing yielded a very compact ...

the Fresnel can have better properties. However, the distortions make them less suitable for imaging where regular lenses still reign supreme. A thinner lens, of course, should let more light ...

But do they actually remove scratches from sunglass lenses? I tried several DIY methods to see if any of them could restore my glasses to their former glory. Do the diy solutions work? Not really.