Folded optics is an optical system in which the beam is bent in a way to make the optical path much longer than the size of the system. This allows the resulting

focal length The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foca ...

of the objective to be greater than the physical length of the optical device.

Prismatic An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled — elements with two parallel surfaces are ''not'' prisms. The most familiar type of opti ...

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes ( binocular vision) when viewing distant objects. Most binoculars are sized to be hel ...

are a well-known example. An early conventional

film camera A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie s ...

(35 mm) was designed by Tessina that used the concept of folded optics. Fold mirrors are used to direct infrared light within the optical path of the

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble ...

. These optical fold mirrors are not to be confused with the observatory's deployable primary mirrors, which are folded inward to fit the telescope within the

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...

's payload fairing; when deployed, these segments are part of the

three-mirror anastigmat 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, and astigmatism. This is primarily used to enable wide fields of v ...

design's primary element and don't serve as fold mirrors in the optical sense.

References

External links

* — Origami Lens Optics {{optics-stub