A Fresnel lens is typically used in “light gathering” applications including condenser systems, light emitter, detector setups, magnifiers and in projection lens or illumination systems. The Fresnel lens is comprises of a “series of concentric grooves etched into plastic.” The lightweight and thin construction of these lenses make them ideal for use in myriad applications.
These lenses are used in place of conventional, curved surface optical lenses. The contours in the Fresnel lens acts as individual refracting surfaces by bending parallel light rays into a common focal point. The benefit of this is that while the lens is physically narrow it can focus light in the same way as a traditional conventional optical lens but its smaller, thinner profile allows it to be used in smaller applications than many conventional lenses.
Projection Lenses
The technology behind the development of the Fresnel lens is that, “the direction of propagation of light does not change within a medium (unless scattered).” Rather, light rays only become scattered when they hit the surface of the medium they are shone on. This means that much of the material in the center of a traditional lens increases its weight and absorption into the system and this can lead to fragmentation or distortion of results.
In the 18th century physicists started to experiment with what evolved into the Fresnel lens by cutting grooves into a piece of glass as a way to create rings into a curved profile. The curved profile, it was discovered, changed the properties and results as compared to the results returned by a conventional lens. The Fresnel lens, it was found, offers better focusing performance in many applications. The groove density also provides higher quality images.
When Fresnel lenses were first developed they were made by grinding and polishing glass by hand. Their manufacture evolved to molten glass being poured into molds and in the 20th century injection molding technology allowed for the production of optical quality plastics to make the lenses.
The original creator of the Fresnel lens was French physicist, Augustin-Jean Fresnel, who popularized the lens for use in lighthouses. Their use has evolved into applications including light collection, magnification and light collimation.