Fresnel lenses consist of a series of
concentric grooves etched into plastic. Their thin, lightweight construction,
availability in small as well as large sizes, and excellent light gathering
ability make them useful in a variety of applications. Fresnel lenses are most
often used in light gathering applications, such as condenser systems or
emitter/detector setups. They can also be used as magnifiers or projection
lenses in illumination systems, and image formulation.
A Fresnel (pronounced fray-NEL) lens
replaces the curved surface of a conventional optical lens with a series of
concentric grooves. These contours act as individual refracting surfaces,
bending parallel light rays to a common focal length (Figure 1). As a result, a
Fresnel lens, while physically narrow in profile, is capable of focusing light
similar to a conventional optical lens but has several advantages over its
thicker counterpart.
