Editing Fresnel lens (section)

== Uses ==

=== Illumination ===
[[File:Inchkeith lighthouse Fresnel lens.JPG|thumb|right|upright=0.3|[[Inchkeith]] lighthouse lens and drive mechanism]]
High-quality glass Fresnel lenses were used in lighthouses, where they were considered state of the art in the late 19th and through the middle of the 20th centuries. These lighthouse Fresnel lens systems typically include extra annular [[Prism (optics)|prismatic]] elements, arrayed in faceted domes above and below the central planar Fresnel, in order to catch all light emitted from the light source. The light path through these elements can include an [[internal reflection]], rather than the simple [[refraction]] in the planar Fresnel element.<ref name=Pepper-Fresnel>{{cite web |url=http://www.terrypepper.com/lights/closeups/illumination/fresnel/fresnel.htm |title=The incredible Fresnel lens |first=Terry |last=Pepper |date=December 2, 2007 |website=Seeing The Light |access-date=31 December 2024}}</ref> These lenses conferred many practical benefits upon the designers, builders, and users of lighthouses and their illumination. Among other things, smaller lenses could fit into more compact spaces. Greater light transmission over longer distances, and varied patterns, made it possible to triangulate a position.<ref name=Pepper-Fresnel/><ref>{{cite web |url=https://www.parks.ca.gov/?page_id=22008 |title=The Lens |publisher=California State Parks |website=Pigeon Point Light Station State Historic Park |access-date=31 December 2024}}</ref> Starting in the mid-20th century, most lighthouses have retired glass Fresnel lenses from service and replaced them with much less expensive and more durable [[aerobeacon]]s<ref>{{cite web |url=http://www.terrypepper.com/lights/closeups/illumination/aerobeacon/dcb224.htm |title=The DCB Series Aerobeacon |first=Terry |last=Pepper |date=December 2, 2007 |website=Seeing The Light |access-date=31 December 2024}}</ref><ref>{{cite news |url=https://www.mvtimes.com/2024/03/08/gay-head-light-requires-upgrade/ |title=Auinnah lighthouse undergoing beacon change |first=Daniel |last=Greenman |date=March 8, 2024 |newspaper=Martha's Vineyard Times |access-date=31 December 2024 |quote=The Carlisle & Finch company's 'DCB-224 aerobeacon' lights were produced so that airports could signal to planes. But they also became common in lighthouses nationwide by the middle of the 20th century.}}</ref> or similar systems, including the Vega Industries [[VRB-25]], which contains plastic Fresnel lens panels.<ref>{{cite news |url=https://uslhs.org/sites/default/files/articles_pdf/VRB25_Summer_2009.pdf |title=Vega VRB-25: Last of the Lighthouse Rotating Beacons as We Know Them |first=Bob |last=Trapani Jr. |date=Summer 2009 |work=The Keeper's Log |publisher=U.S. Lighthouse Society |access-date=31 December 2024}}</ref>

[[File:Chevrolet Bel Air 1956 4door Sedan lamp.jpg|thumb|left|upright=0.5|1956 [[Chevrolet Bel Air|Bel Air]], with Fresnel lenses in round headlamp and rectangular marker lamp]]
Perhaps the most widespread use of Fresnel lenses, for a time, occurred in [[automobile]] [[headlamp]]s, where they can shape the roughly parallel beam from the parabolic reflector to meet requirements for dipped and main-beam patterns, often both in the same headlamp unit (such as the European [[H4 lamp|H4]] design). For reasons of economy, weight, and impact resistance, newer cars have dispensed with glass Fresnel lenses for [[Parabolic aluminized reflector|sealed beam]] headlamp units, instead using [[multifaceted reflector]]s with plain [[polycarbonate]] lenses. However, Fresnel lenses continue in wide use in automobile tail, marker, and reversing lights.

[[Image:Colortran Fresnel.JPG|thumb|right|A Fresnel lantern with the lens open to show the ridges]]
Glass Fresnel lenses also are used in lighting instruments for [[theatre]] and [[motion pictures]] (see [[Fresnel lantern]]); such instruments are often called simply ''Fresnels''. The entire instrument consists of a metal housing, a reflector, a lamp assembly, and a Fresnel lens. Many Fresnel instruments allow the lamp to be moved relative to the lens' [[Focus (optics)|focal point]], to increase or decrease the size of the light beam. As a result, they are very flexible, and can often produce a beam as narrow as 7° or as wide as 70°.<ref>Mumm, Robert C., ''Photometrics Handbook'', 2nd&nbsp;Ed., Broadway Press, 1997, p.{{nbsp}}36.</ref> The Fresnel lens produces a very soft-edged beam, so is often used as a wash light. A holder in front of the lens can hold a colored plastic film (''gel'') to tint the light or wire screens or frosted plastic to diffuse it. The Fresnel lens is useful in the making of motion pictures not only because of its ability to focus the beam brighter than a typical lens, but also because the light is a relatively consistent intensity across the entire width of the beam of light.

[[File:Optical Landing System, night, aboard USS Dwight D. Eisenhower (CVN-69).jpg|thumb|[[Optical landing system]] on US Navy aircraft carrier [[USS Dwight D. Eisenhower|USS ''Dwight D. Eisenhower'']]]]

[[Aircraft carrier]]s and naval air stations typically use Fresnel lenses in their [[optical landing system]]s. The "meatball" light aids the pilot in maintaining proper glide slope for the landing. In the center are amber and red lights composed of Fresnel lenses. Although the lights are always on, the angle of the lens from the pilot's point of view determines the color and position of the visible light. If the lights appear above the green horizontal bar, the pilot is too high. If it is below, the pilot is too low, and if the lights are red, the pilot is very low.<ref>{{Cite web |title=Fresnel Lens Optical Landing System |url=https://www.history.navy.mil/content/history/museums/nnam/explore/exhibits/permanent-exhibits/mezzanine/fresnel-lens-optical-landing-system.html |access-date=2022-04-16 |website=NHHC |language=en-US }}</ref>

Fresnel lenses are also commonly used in [[searchlight]]s, [[Spotlight (theatre lighting)|spotlights]], and [[flashlight]]s.

=== Imaging ===
[[File:Magnifying-fresnel-lens.jpg|thumb|right|A plastic Fresnel lens sold as a TV-screen enlarging device]]
[[File:SinclairFTV1fresnellens1.JPG|thumb|The Fresnel lens used in the [[TV80|Sinclair FTV1]] portable CRT TV, which enlarges the vertical aspect of the display only]]

Fresnel lenses are used as simple hand-held [[Magnifying glass|magnifiers]]. They are also used to correct several visual disorders, including ocular-motility disorders such as [[strabismus]].<ref>{{cite journal|mode=cs2 |last1=Shishavanf |first1=Amir Asgharzadeh |last2=Nordin |first2=Leland |last3=Tjossem |first3=Paul |last4=Abramoff |first4=Michael D. |last5=Toor |first5=Fatima |editor3-first=Nikolay I |editor3-last=Zheludev |editor2-first=Mikhail A. |editor2-last=Noginov |editor1-first=Nader |editor1-last=Engheta |title=PMMA-based ophthalmic contact lens for vision correction of strabismus |journal=Metamaterials |series=Metamaterials, Metadevices, and Metasystems 2016 |year=2016 |volume=9918 |pages=99180C |url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9918/1/PMMA-based-ophthalmic-contact-lens-for-vision-correction-of-strabismus/10.1117/12.2237994.short?SSO=1 |publisher=Society of Photo-Optical Instrumentation Engineers |doi=10.1117/12.2237994 |bibcode=2016SPIE.9918E..0CA |s2cid=125689110 |access-date=21 June 2020}}.</ref> Fresnel lenses have been used to increase the visual size of [[CRT display]]s in pocket [[television]]s, notably the [[Sinclair Research Ltd.|Sinclair]] [[TV80]]. They are also used in [[traffic light]]s.

Fresnel lenses are used in left-hand-drive European [[Lorry|lorries]] entering the UK and Republic of Ireland (and vice versa, right-hand-drive Irish and British trucks entering mainland Europe) to overcome the blind spots caused by the driver operating the lorry while sitting on the wrong side of the cab relative to the side of the road the car is on. They attach to the passenger-side window.<ref>{{cite book|mode=cs2 |url=https://books.google.com/books?id=XG4du9fwEUYC&q=vosa%20fresnel%20lenses&pg=PA321|title=Lowe's Transport Manager's and Operator's Handbook 2012|last=Lowe|first=David|date=2011-12-03|publisher=[[Kogan Page Publishers]]|isbn=978-0-7494-6410-3}}.</ref>

Another automobile application of a Fresnel lens is a rear view enhancer, as the [[Wide-angle lens|wide view angle]] of a lens attached to the rear window permits examining the scene behind a vehicle, particularly a tall or bluff-tailed one, more effectively than a [[rear-view mirror]] alone. Fresnel lenses have been used on rangefinding equipment and [[Moving map display|projected map display]] screens.<ref>{{cite web |url=https://rochesteravionicarchives.co.uk/collection/navigation-inertial/projected-map-display |title=Projected Map Display [PMD] |website=Rochester Avionic Archives |access-date=2024-08-17}}</ref>

Fresnel lenses have also been used in the field of popular entertainment. The British rock artist [[Peter Gabriel]] made use of them in his early solo live performances to magnify the size of his head in contrast to the rest of his body, for dramatic and comic effect. In the [[Terry Gilliam]] film ''[[Brazil (1985 film)|Brazil]]'', Fresnel lenses are used as magnifiers for small CRT monitors in the Ministry of Information. The lenses occasionally appear between the actors and the camera, distorting the scale and composition of the scene to humorous effect. In the [[Pixar]] movie [[Wall-E]], the protagonist watches the musical [[Hello, Dolly! (film)|''Hello, Dolly!'']] on an [[iPod]], magnified by a Fresnel lens.

[[Virtual reality]] headsets, such as the [[Meta Quest 2]] and the [[HTC Vive|HTC Vive Pro]] use Fresnel lenses,<ref>{{Cite web |last=Poore |first=Shaun |date=2022-04-21 |title=What Tech is Inside of a VR Headset? (Quest 2 Teardown) |url=https://www.shaunpoore.com/inside-a-vr-headset/ |access-date=2022-10-27 |website=ShaunPoore.com |language=en}}</ref> as they allow a thinner and lighter form factor than regular lenses.<ref>{{Cite web |date=2016-03-08 |title=How Lenses for Virtual Reality Headsets Work |url=https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ |access-date=2022-10-27 |website=VR Lens Lab |language=en-US |archive-date=27 October 2022 |archive-url=https://web.archive.org/web/20221027133146/https://vr-lens-lab.com/lenses-for-virtual-reality-headsets/ |url-status=dead }}</ref> Newer devices, such as the [[Meta Quest Pro]], have switched to a [[pancake lens]] design<ref>{{Cite web |title=Introducing Meta Quest Pro, an Advanced VR Device for Collaboration and Creation |url=https://www.oculus.com/blog/meta-quest-pro-price-release-date/ |access-date=2022-10-27 |website=www.oculus.com |language=en}}</ref> due to its smaller form factor and less [[chromatic aberration]] than Fresnel lenses.<ref>{{Cite web |last=C |first=Mark |date=2022-04-26 |title=The difference between pancakes lenses and current fresnel lenses found on VR headsets |url=https://vr-expert.com/the-difference-between-pancakes-lenses-and-current-fresnel-lenses-found-on-vr-headsets/ |access-date=2022-10-27 |website=VR Expert {{!}} Enterprise VR/AR Hardware Supplier |language=en-GB}}</ref>

Multi-focal Fresnel lenses are also used as a part of [[retinal scan|retina identification]] cameras, where they provide multiple in- and out-of-focus images of a fixation target inside the camera. For virtually all users, at least one of the images will be in focus, thus allowing correct eye alignment.

Many cameras are equipped with viewfinders which project the scene through a lens onto a [[ground glass]] screen for focusing and composition, including [[view camera|view]], [[twin-lens reflex camera|twin-lens reflex]], and [[single-lens reflex camera]]s; often a Fresnel condenser lens is applied to the ground glass to increase the perceived brightness of the projected image and make the illumination more even from center to corner.<ref>{{cite book |url=https://archive.org/details/usingviewcamera00simm/page/28/mode/2up |title=Using the view camera |first=Steve |last=Simmons |date=1987 |publisher=Amphoto |isbn=0-8174-6347-X |page=29 |url-access=registration}}</ref><ref>{{cite book |url=https://archive.org/details/minoltaguide0000wolf/page/22/mode/2up |title=The Minolta Guide |first=John |last=Wolf |date=1979 |publisher=Amphoto |isbn=0-8174-2453-9 |lccn=78-21451 |page=23 |url-access=registration |quote=The matte screens all have fine-ground translucent surfaces, on which the image from the mirror is projected. These have a Fresnel or field lens, and condenser, which direct light from all parts of the screen's surface to the eyepiece uniformly, creating an image with corner-to-corner brightness.}}</ref> For example, the [[Polaroid SX-70]] camera uses a Fresnel reflector as part of its viewing system.<ref>{{cite journal |doi=10.1364/AO.21.000196 |title=Unusual optics of the Polaroid SX-70 Land camera |first=William T. |last=Plummer |journal=Applied Optics |volume=21 |date=1982 |issue=2 |pages=196–202|pmid=20372431 |bibcode=1982ApOpt..21..196P }}</ref>

==== Projection ====
[[Image:OHP-sch.JPG|thumb|right|An overhead projector in use]]
The use of Fresnel lenses for image projection reduces image quality, so they tend to occur only where quality is not critical or where the bulk of a solid lens would be prohibitive. Cheap Fresnel lenses can be stamped or molded of transparent plastic and are used in [[overhead projector]]s and [[projection television]]s.

Fresnel lenses of different focal lengths (one [[collimator]], and one collector) are used in commercial and [[DIY]] projection. The collimator lens has the lower focal length and is placed closer to the light source, and the collector lens, which focuses the light into the triplet lens, is placed after the projection image (an [[active matrix LCD]] panel in [[LCD projector]]s). Fresnel lenses are also used as collimators in [[overhead projector]]s.

=== Solar power ===
[[File:Luftaufnahme PE 1.JPG|thumb|Solar power plant based on linear Fresnel lenses]]
Since plastic Fresnel lenses can be made larger than glass lenses, as well as being much cheaper and lighter, they are used to concentrate sunlight for heating in [[solar cooker]]s, in solar forges, and in [[Solar thermal collector|solar collectors]] used to heat water for domestic use.<ref>{{cite book |url=https://archive.org/details/directuseofsunse0000dani_b8v1/page/66/mode/2up |title=Direct use of the sun's energy |first=Farrington |last=Daniels |date=1964 |page=66 |publisher=Yale University Press |location=New Haven |isbn=0-300-00399-4 |lccn=64-20913 |url-access=registration |quote=Another device for focusing solar energy is the Fresnel lens. A nest of circular grooves is cut in a sheet of transparent plastic with the sides of each successive ring set in such a way that the light passing through each groove is refracted at a slightly different angle and converges on a point. Such lenses have been pressed out in plastic sheets and they are effective in giving a sharp focus.}}</ref> They can also be used to generate steam or to power a [[Stirling engine]] to generate electricity.<ref>{{cite journal |url=https://archive.org/details/Prt3A978-1-4419-0851-32F2/1-s2.0-S0196890413004494-main/ |title=Performance testing of a Fresnel/Stirling micro solar energy conversion system |first1=Fatih |last1=Aksoy |first2=Halit |last2=Karabulut |date=November 2013 |journal=Energy Conversion and Management |volume=75 |pages=629–634 |doi=10.1016/j.enconman.2013.08.001|bibcode=2013ECM....75..629A }}</ref>

Fresnel lenses can concentrate sunlight onto [[solar cell]]s with a ratio of almost 500:1.<ref>{{cite web|mode=cs2 |url=http://www.soitec.com/en/technologies/concentrix/ |title=Soitec's Concentrix technology |access-date=3 September 2013 | url-status = dead |archive-url=https://web.archive.org/web/20110417051836/http://www.soitec.com/en/technologies/concentrix/ |archive-date=17 April 2011}}.</ref> This allows the active solar-cell surface to be reduced, lowering cost and allowing the use of more efficient cells that would otherwise be too expensive.<ref>{{ cite web| mode = cs2 | title = Soitec's high-performance Concentrix technology | url = http://www.soitec.com/en/technologies/concentrix/components/ | access-date = 27 February 2021 | url-status = dead | archive-url = https://web.archive.org/web/20130923032544/http://www.soitec.com/en/technologies/concentrix/components/ | archive-date = 23 September 2013}}.</ref> In the early 21st century, Fresnel reflectors began to be used in [[concentrating solar power]] (CSP) plants to concentrate solar energy. One application was to preheat water at the coal-fired [[Liddell Power Station]], in Hunter Valley Australia.

Fresnel lenses can be used to [[Sintering|sinter]] sand, allowing [[3D printing]] in glass.<ref>{{cite web|mode=cs2 |author=M. Margolin |url=https://www.vice.com/en/article/this-3d-printer-runs-on-sand-and-sun/ |title=This 3D printer runs on sand and sun |work=Vice |date=24 August 2016 |access-date=2021-02-27 |url-status=live |archive-url=https://web.archive.org/web/20171201182205/https://motherboard.vice.com/en_us/article/wnxpe9/this-3d-printer-runs-on-sand-and-sun|archive-date=1 December 2017}}.</ref>