Magnifying Plastic Sheets, Fresnel
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Fresnel is a thin sheet of plastic engineered so that it becomes a magnifier. They can be tiny (the size of a credit card) or huge (the size of a page). The quality of these is NOT as good as traditional lenses.
Fascinating fact: it's pronounced "Fren-nel" because it's French, after Augustus-Jean Fresnel who invented them (made of glass) for use in lighthouses.