Fresnel lenses consist of a series of concentric grooves etched onto one surface. Their thin, lightweight construction, available in small as well as large sizes, and excellent light gathering ability make them useful in a variety of applications. They are most often used in light gathering applications, such as condenser systems or emitter/detector setups.
The grooves in a Fresnel lens act as individual refracting surfaces, much like a group of tiny prisms. The grooved surfaces replace the continuous surface of a conventional lens into a set of surfaces with the same curvature.
The Fresnel lens allows the construction of large-size and small optical focal length lenses without the bulk: the thickness and weight of the material needed to build them are lower than in a conventional spherical lens of equivalent dioptric power.
The groove density of a lens is measured in the number of grooves per millimeter. Higher groove density (more grooves per millimeter) results in a better quality of the images with lower optical efficiency, while the lower density of the lenses yield a better efficiency with poorer images. Low density lenses are most suitable for light gathering applications, while high density lenses are more suitable for imaging and projection.
Fresnel Lenses datasheet
These lenses are made of polyurethane optical, called REVO-01, which is a material developed by IODA in collaboration with Acomon (a Japanese multinational leader in ophthalmic monomers). This material allows the lens to last over time, being UV-resistant, and makes it suitable for both indoors and outdoors usages.
Augustin-Jean Fresnel — an early 19th century pioneer in the field of wave optics — is credited with the invention and application of grooved lenses. While working as a commissioner of lighthouses in France, Fresnel discovered that grooved lenses captured more oblique light than the conventional ones, allowing lighthouses to operate more efficiently, using even less material for the lenses, and showing light more visible over a greater distance.