Slide projectors display images with an incredible contrast ratio and allow us to create pictures using simple materials such as paper. This is projector is as simple as it gets, an LED light source, a convex lens (from a magnifying glass) and a projection lens of eBay.It might be a good idea to test all the components together before cutting the pieces. I used a 100mm projection lens, so any other focal length might result in different distances within the system. The ones used here are:Be careful to use a light source that does not get too hot, I used an LED lamp. However, one should try and find one above 500 lumens and with as less LEDs as possible, as more than one LED results in an unevenly lit projection.