Fresnel

Part of speech: adjective

Definitions

1. A specialized lens characterized by a series of stepped grooves that enable efficient light focusing despite its reduced thickness
2. An optical component designed to reduce bulk while retaining functionality, often employed in lighting and projection systems
3. A unique type of lens that features concentric grooves to focus light effectively while minimizing the material thickness needed for its construction

Etymology: The Fresnel lens is named after Augustin-Jean Fresnel, a French physicist who developed it in the late 1810s and early 1820s while studying the wave nature of light. He realised that a conventional thick lens could be sliced into concentric rings, each bent to focus light in the same direction, so the glass could be made almost flat. This made lighthouse optics far lighter and cheaper, since a very large lens could be built without the enormous weight of solid glass. The term is a surname turned into an adjective, a common pattern in technical English, so the name itself tells the story. Fresnel's name now attaches to a whole family of thin, stepped optical elements, and the word is used in that sense rather than for his particular person.