Who says good deeds aren’t their own reward? Last Sunday I was visiting my mother to help here move some heavier thing out of her garage. Among the victims of our cleaning day was one very large, but very dead big screen television. The original plan was to roll it up to the street where, if somone didn’t take it, the very enthusiastic sanitation department would get to it in a few days. It dawned upon me that there was still some life in this appliance yet, however.
You see, before you young whipper-snappers and your plasma hdtv, fusion whatchamacallits there were projection televsions. These huge things would project an image produced from a three color channel bulbs with a series of mirrors and a large flat lens, called a fresnel lens.
Fresnel lens in themselves are mighty clever and wondorous things. They originated from the need to focus and direct large quantities of light without a truly monumental size traditional lens. Many antique as well as functional ones can be found in lighthouses to this day.
Fresnel lens can also still be found as page magnifiers, overhead projectors and what not where the advantages of a flat lens with a high optical volume is desireable. As a matter of fact I have a small one, I’ve mounted in an armature that I’ve used to do some trivial solar cooking and melting softer metals (like lead). It is only about ten inches across. The fresnel lens I removed from the television is three feet across! Needless to say, once I build an armature, get some welding goggles and the weather clears many a penny or patch of asphalt will be subjected to my curiousity.