Reading on Fresnel Lenses

Fresnel Lenses

During the height of the Shipping Age in the 18th century, France was looking for a way to make new lighthouses along the coast of Normandy and Brittany. The lenses that were used in the lighthouses were huge pieces of glass that were both bulky and expensive. In 1748, Georges de Buffon realized that only one side of a lens is needed to bend light. In fact, only the outer surface of the lens is needed. Light is bent at the lens/air boundary.

de Buffon cut away the inside of the lens and left rings with edges on the outside. Later, Augustin Fresnel modified this idea and the modern Fresnel lens was created. His lenses were first used on the French coast as a lightweight and less-expensive alternative to the old, bulky lighthouse lenses.

Below is a schematic cut-away diagram showing how a Fresnel lens is made.

Fresnel lenses are lighter than conventional convex lenses. The Fresnel lens can have the same focal length as a conventional lens so both can have the same magnification. The image quality is not as good in the Fresnel lens as in the conventional lens. When plastic is used as is the case for the Fresnel lens in the Optics Kit, the quality of the image is further degraded over that of a quartz lens.