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A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x).The lens focuses light in the same way as a conventional lens. Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradient of the refractive index of a material.
A Paul design has a parabolic primary with spherical secondary and tertiary mirrors; a Paul–Baker design modifies the secondary slightly to flatten the focal plane. A three-mirror anastigmat is an anastigmat telescope built with three curved mirrors, enabling it to minimize all three main optical aberrations – spherical aberration , coma ...
The saw-tooth lens is a unique optical scheme suggested and demonstrated by Cederstrom. [6] It approximates a parabolic lens much as a numerical computation on a grid approximates a smooth line, with a series of prisms that each deflect the X-rays over a minute angle. Lenses of this type have been made from silicon, plastic, and lithium.
A variation on the Luneburg lens antenna is the hemispherical Luneburg lens antenna or Luneburg reflector antenna. This uses just one hemisphere of a Luneburg lens, with the cut surface of the sphere resting on a reflecting metal ground plane. The arrangement halves the weight of the lens, and the ground plane provides a convenient means of ...
A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid , that is, the surface generated by a parabola revolving around its axis.
A Fresnel lens (/ ˈ f r eɪ n ɛ l,-n əl / FRAY-nel, -nəl; / ˈ f r ɛ n ɛ l,-əl / FREN-el, -əl; or / f r eɪ ˈ n ɛ l / 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.
These reflectors make use of the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length while simultaneously reducing the volume of material required for the reflector. This greatly reduces the system's cost since sagged-glass parabolic reflectors are typically very expensive. [2]
The most common non-spherical type are parabolic reflectors, found in optical devices such as reflecting telescopes that need to image distant objects, since spherical mirror systems, like spherical lenses, suffer from spherical aberration. Distorting mirrors are used for entertainment. They have convex and concave regions that produce ...