Fresnel lenses are formed of a series of concentric annular grooves that have a common focus. The grooves are located on the plane of the lens, making it exceptionally flat compared to refractive lenses that have analogous f-number (Fresnel Lenses 2). It was known hundreds of years ago that focusing properties of a lens are being defined by its contour. Therefore, the optical properties of the lens do not depend on most of the material that lies between the refracting surfaces (Fresnel Lenses 2). In the Fresnel lens, absorption losses are being decreased by extracting annular cylinders of lens material (Fresnel Lenses 2). Right circular cylindrical parts of the lens form its contour and are being intersected by a series of inclined surfaces called grooves (Fresnel Lenses 2). The inclined portions of the lens are almost parallel to the center and very steep toward the outer edge. They act as many refracting surfaces that bend a series of parallel light rays to a common focal length. Even though Fresnel lenses have a physically narrower profile than curved refractive lenses, they can focus light in a similar way (Fresnel Lenses 2).
The earliest design of a stepped-surface lens was developed by Count Buffon in 1748 (Fresnel Lenses 2). He suggested reducing the plano side material of the lens along its spherical surface so it would become thinner. Condorcet and Sir D. Brewster improved Buffon’s idea and suggested their designs of built-up lenses with a stepped surface (Fresnel Lenses 2). The French civil engineer Augustin Jean Fresnel invented the aspheric lens in 1822 (Fresnel Lenses 2). He worked in Paris in the department of civil engineering responsible for building lighthouses. At that time, there were many lighthouses on every European coastline; however, visibility of their lights was extremely low, so many ships’ captains could not steer their vessels away from rocks (Driggers 616). Fresnel was assigned to construct a lens that would make the visibility of lighthouses much higher and, thus, would save many lives. In order to create such lens, he had to resolve the disagreement between the two theories of light: corpuscular and wave (Driggers 616).
The first Fresnel lens was installed in a lighthouse located on the bank of the river Gironde (Fresnel Lenses 2). Spherical aberration was almost eliminated in Fresnel’s design by making the center of curvature of each groove recede towards the center of the lens. The first Fresnel lenses were cut from glass and subsequently polished (Fresnel Lenses 3). It was an expensive way of lens manufacturing that significantly limited their mass production. This way of producing lenses changed only in the early 1950s with the arrival of the technique of molding that made them relatively inexpensive (Fresnel Lenses 3). In the subsequent forty years, the emergence of optical-quality plastics aided by the injection molding and computer-controlled compression have made the mass scale manufacturing of first-class lenses possible.
Modern plastic lenses surpass the quality of even the finest glass Fresnel lenses by far (Fresnel Lenses 3). They are being made of acrylic, rigid vinyl and polycarbonate—the materials suitable for visible light and infrared light applications (Fresnel Lenses 4). Fresnel Lens can be used in collimators, collectors, condensers, field lenses, magnifiers, Fresnel screen brighteners, magnifiers, near-infrared applications, passive infrared applications, process monitoring at 3.4 µm, imaging and special optics among others (Fresnel Lenses 8).
Works Cited
Driggers, Ronald G. Ed. Encyclopedia of Optical Engineering. New York: Marcel Dekker, 2003. Print.
Fresnel Lenses. High Quality Fresnel Lenses in a Variety of Sizes & Focal Lengths. 2016. Web.