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A Fresnel lens ( / ˈfreɪnɛl, - nəl / FRAY-nel, -nəl; / ˈfrɛnɛl, - əl / FREN-el, -əl; or / freɪˈnɛl / fray-NEL [1]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.
The Peli Lens is a mobility aid for people with homonymous hemianopia. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in 1999. It expands the visual field by 20 degrees.
The Fresnel equations (or Fresnel coefficients) describe the reflection and transmission of light (or electromagnetic radiation in general) when incident on an interface between different optical media.
Some micro-lenses achieve their focusing action by both a variation in refractive index and by the surface shape. Another class of microlens, sometimes known as micro-Fresnel lenses, focus light by refraction in a set of concentric curved surfaces. Such lenses can be made very thin and lightweight. Binary-optic micro-lenses focus light by ...
By the 1950s, the substitution of plastic for glass made it economic to use fine-stepped Fresnel lenses as condensers in overhead projectors. Still finer steps can be found in low-cost plastic "sheet" magnifiers.
The lenticular lens in the example above has focal length 342 μm and back focal distance 48 μm, indicating that the focal plane of the lens falls 48 micrometers behind the image printed on the back of the lens. See also. Fresnel lens, a different 'flat' lens technology; Integral imaging; Microlens; References
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