Basic Principle of the Fresnel Lens

The Fresnel lens was invented by the French physicist Augustin-Jean Fresnel, who in 1822 first employed this type of lens to design a glass Fresnel lens system—the lighthouse lens.

The idea of producing lighter, thinner lenses by mounting several individual refracting elements on a common frame is often attributed to the Count de Buffon. Condorcet (1743–1794) proposed grinding such lenses from a single sheet of thin glass, while the French physicist and engineer Augustin-Jean Fresnel also placed great hopes on their application in lighthouses. According to the Smithsonian Institution, in 1823 the first Fresnel lens was installed at the Phare de Cordouan at the mouth of the Gironde River; the light it focused could be seen from as far as 20 miles (32 kilometers) away. Sir David Brewster, a Scottish physicist, is regarded as the driving force behind the adoption of this type of lens in British lighthouses.

Basic Principle

Its operating principle is remarkably simple: assume that the refractive power of a lens is concentrated entirely at its optical surfaces (e.g., the lens surface), and remove as much of the bulk optical material as possible while preserving the curvature of those surfaces.

Another way to understand it is that the continuous surface of the lens “collapses” into a planar configuration. In cross-section, the surface consists of a series of serrated grooves, with an elliptical arc at the center. Each groove is oriented at a different angle relative to its neighbors, yet all converge the light rays to a single point, forming the central focal point—the lens’s focus. Each groove can be regarded as an independent miniature lens, capable of collimating or converging the light. Moreover, this type of lens can also reduce certain spherical aberrations.

Key words:

Fresnel lens