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 ...

If you are a Hackaday reader, you probably know what a Fresnel lens is. You find them in everything from overhead projectors to VR headsets. While it seems commonplace now, the Fresnel lens was an ...