light tube#Light tube with reflective material

File:Copper Box interior.JPG, venue for Handball at the 2012 Summer Olympics, makes use of light tubes to reduce energy use.]]

Manufacturing custom designed infrared light pipes, hollow waveguides and homogenizers is non-trivial. This is because these are tubes lined with a highly polished infrared reflective coating of gold, which can be applied thick enough to permit these tubes to be used in highly corrosive atmospheres. Carbon black can be applied to certain parts of light pipes to absorb IR light (see photonics). This is done to limit IR light to only certain areas of the pipe.

While most light pipes are produced with a round cross-section, light pipes are not limited to this geometry. Square and hexagonal cross-sections are used in special applications. Hexagonal pipes tend to produce the most homogenized type of IR Light. The pipes do not need to be straight. Bends in the pipe have little effect on efficiency.

{{Multiple image

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| header = A light tube installed in the subterranean train station at Potsdamer Platz, Berlin

| image1 = Bahnhof Berlin Potsdamer Platz Lichtröhre Straße Detail.jpg

| caption1 = Capturing sunlight above ground

| image2 = Berlin light tube.jpg

| caption2 = Distributing sunlight below ground

}}

The first commercial reflector systems were patented and marketed in the 1850s by Paul Emile Chappuis in London, utilizing various forms of angled mirror designs. Chappuis Ltd's reflectors were in continuous production until the factory was destroyed in 1943.{{Cite web |title=Image of advertisement for chappuis' patent reflectors, c 1851-1870. by Science & Society Picture Library |url=https://www.scienceandsociety.co.uk/results.asp?image=10422108 |access-date=2022-12-19 |website=www.scienceandsociety.co.uk}} The concept was rediscovered and patented in 1986 by Solatube International of Australia.{{Cite web |title=Solatube Company History {{!}} Our Story & Timeline |url=https://solatube.com.au/solatube-history/ |access-date=2022-12-19 |website=Solatube Australia |language=en-US}} This system has been marketed for widespread residential and commercial use. Other daylighting products are on the market under various generic names, such as "SunScope", "solar pipe", "light pipe", "light tube", and "tubular skylight".

A tube lined with highly reflective material leads the light rays through a building, starting from an entrance-point located on its roof or one of its outer walls. A light tube is not intended for imaging (in contrast to a periscope, for example); thus image distortions pose no problem and are in many ways encouraged due to the reduction of "directional" light.

The entrance point usually comprises a dome (cupola), which has the function of collecting and reflecting as much sunlight as possible into the tube. Many units also have directional "collectors", "reflectors", or even Fresnel lens devices that assist in collecting additional directional light down the tube.

In 1994, the Windows and Daylighting Group at Lawrence Berkeley National Laboratory (LBNL) developed a series of horizontal light pipe prototypes to increase daylight illuminance at distances of 4.6-9.1 m, to improve the uniformity of daylight distribution and luminance gradient across the room under variable sun and sky conditions throughout the year. The light pipes were designed to passively transport daylighting through relatively small inlet glazing areas by reflecting sunlight to depths greater than conventional sidelight windows or skylights.LBNL: [https://escholarship.org/content/qt393602kq/qt393602kq.pdf The Design and Evaluation of Three Advanced Daylighting Systems: Light Shelves, Light Pipes and Skylights]{{Cite journal |last1=Beltrán |first1=L.O. |last2=Lee |first2=E.S. |last3=Selkowitz |first3=S.E. |date=July 1997 |title=Advanced Optical Daylighting Systems: Light Shelves and Light Pipes |url=http://www.tandfonline.com/doi/abs/10.1080/00994480.1997.10748194 |journal=Journal of the Illuminating Engineering Society |language=en |volume=26 |issue=2 |pages=91–106 |doi=10.1080/00994480.1997.10748194 |s2cid=112083025 |issn=0099-4480|hdl=1969.1/160504 |hdl-access=free }}

A set-up in which a laser cut acrylic panel is arranged to redirect sunlight into a horizontally or vertically orientated mirrored pipe, combined with a light spreading system with a triangular arrangement of laser cut panels that spread the light into the room, was developed at the Queensland University of Technology in Brisbane.Ken Yeang: [http://www.trhamzahyeang.com/features/img/Light%20pipe%20paper.pdf Light Pipes: An Innovative Design Device for Bringing Natural Daylight and Illumination into Buildings with Deep Floor Plan] {{webarchive|url=https://web.archive.org/web/20090305001322/http://www.trhamzahyeang.com/features/img/Light%20pipe%20paper.pdf |date=2009-03-05 }}, Nomination for the Far East Economic Review Asian Innovation Awards 2003 In 2003, Veronica Garcia Hansen, Ken Yeang, and Ian Edmonds were awarded the Far East Economic Review Innovation Award in bronze for this development.[http://www.scienceinpublic.com/freshinnovators/2005/Veronica/veronicagarciahansen.htm Lighting up your workplace — Queensland student pipes light to your office cubicle] {{webarchive|url=https://web.archive.org/web/20090105210012/http://www.scienceinpublic.com/freshinnovators/2005/Veronica/veronicagarciahansen.htm |date=2009-01-05 }}, May 9, 2005[http://www.worldcities.com.sg/speaker3.htm#kenneth01 Kenneth Yeang] {{webarchive|url=https://web.archive.org/web/20080925033953/http://www.worldcities.com.sg/speaker3.htm |date=2008-09-25 }}, World Cities Summit 2008, June 23–25, 2008, Singapore

Light transmission efficiency is greatest if the tube is short and straight. In longer, angled, or flexible tubes, part of the light intensity is lost. To minimize losses, a high reflectivity of the tube lining is crucial; manufacturers claim reflectivities of their materials, in the visible range, of up to almost 99.5 percent.{{cite web |url=http://www.alanod.de/opencms/sites/alanod.de/de/miro/MIRO_Produkte/MIRO_LIGHTPIPE/index.html |title=MIRO LIGHTPIPE |access-date=2006-08-01 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20061114231516/http://www.alanod.de/opencms/sites/alanod.de/de/miro/MIRO_Produkte/MIRO_LIGHTPIPE/index.html |archive-date=November 14, 2006 }}{{in lang|fr}} [http://www.acoram.biz/frtubelumiere.htm Tube de Lumière] {{webarchive|url=https://web.archive.org/web/20070225034937/http://www.acoram.biz/frtubelumiere.htm |date=2007-02-25 }}

At the end point (the point of use), a diffuser spreads the light into the room.

The first full-scale passive horizontal light pipes were built at the Daylight Lab at Texas A&M University, where the annual daylight performance was thoroughly evaluated in a 360 degree rotating 6 m wide by 10 m deep room. The pipe is coated with a 99.3% specular reflective film and the distribution element at the end of the light pipe consists of a 4.6 m long diffusing radial film with an 87% visible transmittance. The light pipe introduces consistently illuminance levels ranging between 300 and 2,500 lux throughout the year at distances between 7.6 m to 10 m.{{Citation |last=Beltrán |first=Liliana O. |title=Assessing the Lighting Performance of an Innovative Core Sunlighting System |date=2020 |url=https://doi.org/10.1007/978-3-030-37635-2_43 |work=Smart and Sustainable Cities and Buildings |pages=631–641 |editor-last=Roggema |editor-first=Rob |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-37635-2_43 |isbn=978-3-030-37635-2 |s2cid=219493476 |access-date=2022-12-19 |editor2-last=Roggema |editor2-first=Anouk|url-access=subscription }}

To further optimize the use of solar light, a heliostat can be installed which tracks the movement of the sun, thereby directing sunlight into the light tube at all times of the day as far as the surroundings' limitations allow, possibly with additional mirrors or other reflective elements that influence the light path. The heliostat can be set to capture moonlight at night.

Optical fibers can also be used for daylighting. A solar lighting system based on plastic optical fibers was in development at Oak Ridge National Laboratory in 2004.[http://www.ornl.gov/sci/solar/pdfs/Let%20the%20Sun%20Shine%20In.pdf Article on Hybrid Solar Lighting "Let the Sun Shine in", Discover Magazine, Vol. 25, No. 07, July 2004] {{webarchive|url=https://web.archive.org/web/20060809224307/http://www.ornl.gov/sci/solar/pdfs/Let%20the%20Sun%20Shine%20In.pdf |date=2006-08-09 }}[http://www.ornl.gov/sci/solar/ ORNL - Solar Technologies Program] {{webarchive|url=https://web.archive.org/web/20130701184144/http://www.ornl.gov/sci/solar/ |date=2013-07-01 }} The system was installed at the American Museum of Science and Energy, Tennessee, USA, in 2005,HSL Featured in [http://www.popsci.com/popsci/whatsnew/7b1f0e0796b84010vgnvcm1000004eecbccdrcrd.html Popular Science's What's New Section] {{webarchive|url=https://web.archive.org/web/20051217024120/http://www.popsci.com/popsci/whatsnew/7b1f0e0796b84010vgnvcm1000004eecbccdrcrd.html |date=2005-12-17 }} June 2005, Page 28 and brought to market the same year by the company Sunlight Direct.[http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20050830-00 Oak Ridge National Laboratory – New Oak Ridge company putting hybrid solar lighting on map] {{webarchive|url=https://web.archive.org/web/20060928232712/http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20050830-00 |date=2006-09-28 }}[http://www.sunlight-direct.com/overview.html Sunlight Direct- Architectural Design Information] {{webarchive|url=https://web.archive.org/web/20060819054131/http://www.sunlight-direct.com/overview.html |date=2006-08-19 }} However, this system was taken off the market in 2009.

In view of the usually small diameter of the fibers, an efficient daylighting set-up requires a parabolic collector to track the sun and concentrate its light.

Optical fibers intended for light transport need to propagate as much light as possible within the core; in contrast, optical fibers intended for light distribution are designed to let part of the light leak through their cladding.[http://ncr101.montana.edu/Light1994Conf/6_8_Kozai/Kozai%20Fiber%20text.htm Use Of Diffusive Optical Fibers For Plant Lighting] {{webarchive|url=https://web.archive.org/web/20060907235120/http://ncr101.montana.edu/Light1994Conf/6_8_Kozai/Kozai%20Fiber%20text.htm |date=2006-09-07 }}

Optical fibers are also used in the Bjork system sold by Parans Solar Lighting AB.[http://www.buildinggreen.com/live/index.cfm/2010/3/3/Alexs-Cool-Product-of-the-Week-FiberOptic-Daylighting-from-Parans Parans Bjork] {{webarchive|url=https://web.archive.org/web/20110708104119/http://www.buildinggreen.com/live/index.cfm/2010/3/3/Alexs-Cool-Product-of-the-Week-FiberOptic-Daylighting-from-Parans |date=2011-07-08 }}[http://inhabitat.com/sunlight-transport-system/ Parans Bjork system review by Inhabitat] {{webarchive|url=https://web.archive.org/web/20101126144823/http://inhabitat.com/sunlight-transport-system/ |date=2010-11-26 }} The optic fibers in this system are made of PMMA (PolyMethyl MethAcrylate) and sheathed with Megolon, a halogen-free thermoplastic resin. A system such as this, however, is quite expensive.[http://www.buildinggreen.com/live/index.cfm/2010/3/3/Alexs-Cool-Product-of-the-Week-FiberOptic-Daylighting-from-Parans Typical system starting at $10,000] {{webarchive|url=https://web.archive.org/web/20110708104119/http://www.buildinggreen.com/live/index.cfm/2010/3/3/Alexs-Cool-Product-of-the-Week-FiberOptic-Daylighting-from-Parans |date=2011-07-08 }}

The Parans system{{Cite web|url=https://parans.com/wp-content/themes/parans/assets/pdf/Parans-Light-Guide.pdf|title=Parans Light Guide}} consists of three parts. A collector, fiber optic cables, and luminaires spreading the light indoors. One or more collectors are placed on or near the building in a place where they will have good access to direct sunlight. The collector consists of lenses mounted in aluminum profiles with a covering glass as protection. These lenses concentrate sunlight down in the fiber optic cables.

The collectors are modular, which means they come with either 4,6,8,12 or 20 cables depending on the need. Every cable can have an individual length. The fiber optic cables transport the natural light 100 meters (30 floors) in and through the property while retaining both a high level of light quality and light intensity. Examples of implementations are Kastrup Airport, University of Arizona and Stockholm University.

A similar system, but using optical fibers of glass, had earlier been under study in Japan.[https://web.archive.org/web/20150109220636/http://www.nbcnews.com/id/7287168 Hybrid Solar Lighting: Bringing a little sunshine into our lives], NBC News, March 2005

Corning Inc. makes Fibrance Light-Diffusing Fiber. Fibrance works by shining a laser through a light-diffusing fiber optic cable. The cable gives off a lighted glow.[https://www.corning.com/worldwide/en/products/advanced-optics/product-materials/specialty-fiber/light-diffusing-fiber2.html Corning Fibrance official website]

Optical fibers are used in fiberscopes for imaging applications.

A prism light guide was developed in 1981 by Lorne Whitehead, a physics professor at the University of British Columbia,[https://www.theglobeandmail.com/news/technology/science/switch-off-the-lights-here-comes-the-sun/article2317875/ Switch off the lights, here comes the sun] {{webarchive|url=https://web.archive.org/web/20120330011229/http://www.theglobeandmail.com/news/technology/science/switch-off-the-lights-here-comes-the-sun/article2317875/ |date=2012-03-30 }} Toronto Globe and Mail, 2012 January 28[http://ncr101.montana.edu/Light1994Conf/6_6_Kneipp/Kneipp%20text.htm Use Of Prismatic Films To Control Light Distribution] {{webarchive|url=https://web.archive.org/web/20060907234851/http://ncr101.montana.edu/Light1994Conf/6_6_Kneipp/Kneipp%20text.htm |date=2006-09-07 }} and has been used in solar lighting for both the transport and distribution of light.[http://www.physics.ubc.ca/ssp/research/solarlighting.htm Solar Canopy Illumination: Solar Lighting at UBC] {{webarchive|url=https://web.archive.org/web/20070911220322/http://www.physics.ubc.ca/ssp/research/solarlighting.htm |date=2007-09-11 }}[http://www.physics.ubc.ca/ssp/ssp_research.htm#lightpipe research frame] {{webarchive|url=https://web.archive.org/web/20051103033059/http://www.physics.ubc.ca/ssp/ssp_research.htm |date=2005-11-03 }} A large solar pipe based on the same principle was set up in the narrow courtyard of a 14-floor building of a Washington, D.C. law firm in 2001,[http://www.detail.de/Archiv/En/HoleArtikel/5331/Artikel Solar Light Pipe in Washington, D.C.] {{webarchive|url=https://web.archive.org/web/20060220221813/http://www.detail.de/Archiv/En/HoleArtikel/5331/Artikel |date=2006-02-20 }}[http://www.idonline.com/adr03/solar_contemp_eco.asp IDOnline.com - The International Design Magazine - Graphic Design, Product Design, Architecture] {{webarchive|url=https://web.archive.org/web/20060905052230/http://www.idonline.com/adr03/solar_contemp_eco.asp |date=2006-09-05 }}{{cite web |url=http://www.bomin-solar.de/Acrobat/Heliostat/H-4158-USA-Washington-SLP-2001.pdf |title=Archived copy |access-date=2006-08-03 |url-status=live |archive-url=https://web.archive.org/web/20060928025611/http://www.bomin-solar.de/Acrobat/Heliostat/H-4158-USA-Washington-SLP-2001.pdf |archive-date=2006-09-28 }}{{cite web |url=http://www.bomin-solar.de/Acrobat/Press/DETAIL_4-04_SLP-Washington.pdf |title=Archived copy |access-date=2006-08-03 |url-status=live |archive-url=https://web.archive.org/web/20060928023025/http://www.bomin-solar.de/Acrobat/Press/DETAIL_4-04_SLP-Washington.pdf |archive-date=2006-09-28 |language=de}}[http://www.detail.de/rw_5_Archive_En_HoleArtikel_5331_Artikel.htm "Solar Light Pipe in Washington, D.C.", DETAIL 4/2004, Building with light] {{webarchive|url=https://web.archive.org/web/20070312052445/http://www.detail.de/rw_5_Archive_En_HoleArtikel_5331_Artikel.htm |date=2007-03-12 }} and a similar proposal has been made for London.[http://carpenterlowings.com/clad_projects_regent%20street.htm Apple London – Special Ceiling] {{webarchive|url=https://web.archive.org/web/20060622051413/http://carpenterlowings.com/clad_projects_regent%20street.htm |date=2006-06-22 }} A further system has been installed in Berlin.{{in lang|de}} [http://www.energie.gr.ch/merkblatter/faktorlicht04.pdf "Tageslicht aus der Tube", Faktor Licht, Nr. 4, 2003] {{webarchive|url=https://web.archive.org/web/20061105235559/http://www.energie.gr.ch/merkblatter/faktorlicht04.pdf |date=2006-11-05 }} (with a description of the light pipe on Potsdamer Platz, Berlin)

The 3M company developed a system based on optical lighting film[http://www.mmm.com/intl/CH/english/archive/story4_980326.html Heliobus with 3M Optical Lighting Film (OLF)] {{webarchive|url=https://web.archive.org/web/20060906060528/http://www.mmm.com/intl/CH/english/archive/story4_980326.html |date=2006-09-06 }} and developed the 3M light pipe,[http://cms.3m.com/cms/US/en/2-197/krcziFU/view.jhtml 3M Light Management Solutions (US)] {{webarchive|url=https://web.archive.org/web/20031119080804/http://cms.3m.com/cms/US/en/2-197/krcziFU/view.jhtml |date=2003-11-19 }} which is a light guide designed to distribute light uniformly over its length, with a thin film incorporating microscopic prisms, which has been marketed in connection with artificial light sources, e.g. sulfur lamps.

In contrast to an optical fiber which has a solid core, a prism light guide leads the light through air and is therefore referred to as a hollow light guide.

The project ARTHELIO,{{cite web |url=http://erg.ucd.ie/enerbuild/pdfs/ARTHELIO.pdf |title=Archived copy |access-date=2006-08-05 |url-status=live |archive-url=https://web.archive.org/web/20070713094620/http://erg.ucd.ie/enerbuild/pdfs/ARTHELIO.pdf |archive-date=2007-07-13 }}{{cite web|url=http://www.iuav.it/Didattica1/pagine-web/facolt--di/Antonio-Ca/master-pro/Lux-Europa-2001.PDF|title=An innovative system for daylight collection and transport for long distances and mixing with artificial light coming from hollow light guides|last1=Mingozzi|first1=Angelo|last2=Bottiglioni|first2=Sergio|archive-url=https://web.archive.org/web/20070930192248/http://www.iuav.it/Didattica1/pagine-web/facolt--di/Antonio-Ca/master-pro/Lux-Europa-2001.PDF|archive-date=30 September 2007}} partially funded by the European Commission, was an investigation in years 1998 to 2000 into a system for adaptive mixing of solar and artificial light, and which includes a sulfur lamp, a heliostat, and hollow light guides for light transport and distribution.

Disney has experimented with using 3D printing to print internal light guides for illuminated toys.{{Cite news

|title = Disney develops 3D-printed lighting for toys

|url = https://www.bbc.co.uk/news/technology-19818815

|date = 3 October 2012

|publisher = BBC News Online

|url-status = live

|archive-url = https://web.archive.org/web/20121004123009/http://www.bbc.co.uk/news/technology-19818815

|archive-date = 4 October 2012

}}

In a system developed by Fluorosolar and the University of Technology, Sydney, two fluorescent polymer layers in a flat panel capture short wave sunlight, particularly ultraviolet light, generating red and green light, respectively, which is guided into the interior of a building. There, the red and green light is mixed with artificial blue light to yield white light, without infrared or ultraviolet. This system, which collects light without requiring mobile parts such as a heliostat or a parabolic collector, is intended to transfer light to any place within a building. [http://www.fluorosolar.com Fluorosolar] {{webarchive|url=https://web.archive.org/web/20070112181728/http://www.fluorosolar.com/ |date=January 12, 2007 }}[http://www.treehugger.com/files/2006/05/fluorosolar_bri.php FluoroSolar - Bringing the Sunshine Inside] {{webarchive|url=https://web.archive.org/web/20070506233137/http://www.treehugger.com/files/2006/05/fluorosolar_bri.php |date=2007-05-06 }}, Treehugger, February 5, 2006 (retrieved on January 13, 2007)[http://www.abc.net.au/catalyst/stories/s1610451.htm Video] {{webarchive|url=https://web.archive.org/web/20070202092336/http://www.abc.net.au/catalyst/stories/s1610451.htm |date=2007-02-02 }} on fluorescence based system By capturing ultraviolet, the system can be especially effective on bright but overcast days; this is since ultraviolet is diminished less by cloud cover than are the visible components of sunlight.

File:Solatube 160 DS rafter cutaway.jpg

Solar light pipes, compared to conventional skylights and other windows, offer better heat insulation properties and more flexibility for use in inner rooms, but less visual contact with the external environment.

In the context of seasonal affective disorder, it may be worth considering that an additional installation of light tubes increases the amount of natural daily light exposure. It could thus possibly contribute to residents´ or employees´ well-being while avoiding over-illumination effects.

Compared to artificial lights, light tubes have the advantage of providing natural light and of saving energy. The transmitted light varies over the day; should this not be desired, light tubes can be combined with artificial light in a hybrid set-up.[http://www.sunpipe.com/NightLite.htm Night Lite] {{webarchive|url=https://web.archive.org/web/20060805125652/http://www.sunpipe.com/NightLite.htm |date=2006-08-05 }}{{cite web |url=http://www.natural-light-skylights.com/pages/light_kit.html |title= Light_kit|website=www.natural-light-skylights.com |archive-url=https://web.archive.org/web/20060818184743/http://www.natural-light-skylights.com/pages/light_kit.html |archive-date=August 18, 2006}}[http://www.sunlight-direct.com/lighting.html Sunlight Direct- Lighting Design Information] {{webarchive|url=https://web.archive.org/web/20060721144112/http://www.sunlight-direct.com/lighting.html |date=2006-07-21 }}

Some artificial light sources are marketed which have a spectrum similar to that of sunlight, at least in the human visible spectrum range,[http://www.xternet.de/bioelektrik/en/true-lite.htm True-Lite] {{webarchive|url=https://archive.today/20020108115037/http://www.xternet.de/bioelektrik/en/true-lite.htm |date=2002-01-08 }}{{cite web |url=http://www.solux.net/ |title=What is SoLux? |publisher=Solux.net |access-date=2010-09-29 |url-status=live |archive-url=https://web.archive.org/web/20080706120915/http://solux.net/ |archive-date=2008-07-06 }}{{cite web |url=http://www.e-wenzl.at/lichtliteratur/vollspektrum_001.html |title=Biolight, Truelite, Vollspektrum Tageslichtlampen, Tageslichtröhren, Tageslichtröhre, Tageslichtspot, Gesundheit mit Licht |access-date=2006-08-02 |url-status=live |archive-url=https://web.archive.org/web/20110531205333/http://www.e-wenzl.at/lichtliteratur/vollspektrum_001.html |archive-date=2011-05-31 |language=de}} as well as low flicker. Their spectrum can be made to vary dynamically such as to mimic changes in natural light over the day. Manufacturers and vendors of such light sources claim that their products can provide the same or similar health effects as natural light.{{cite web|url=http://www.j-lorber.de/shm/licht/vollspektrum-bedeutg.htm |title=Ausgleich von fehlenden Photonen und Sonnenlichtfrequenzen |access-date=2006-08-02 |url-status=dead |archive-url=https://web.archive.org/web/20060625161813/http://j-lorber.de/shm/licht/vollspektrum-bedeutg.htm |archive-date=2006-06-25 |language=de}}{{cite web |url=http://www.villiton.ch/vollspektrumlicht.php |title=Villiton - Biolicht - Bio-Licht Vollspektrum-Bio-Licht Tageslicht-Röhren True-Lite Bio-Light natürliches Licht |access-date=2006-08-02 |url-status=live |archive-url=https://web.archive.org/web/20060615171028/http://www.villiton.ch/vollspektrumlicht.php |archive-date=2006-06-15 |language=de}} When considered as alternatives to solar light pipes, such products may have lower installation costs but do consume energy during use; therefore they may well be more wasteful in terms of overall energy resources and costs.

On a more practical note, light tubes do not require electric installations or insulation and are thus especially useful for indoor wet areas such as bathrooms and pools. From a more artistic point of view, recent developments, especially those pertaining to transparent light tubes, open new and interesting possibilities for architectural lighting design.{{Citation needed|date=June 2021}}

Due to the relatively small size and high light output of sun pipes, they have an ideal application to security-oriented situations, such as prisons, police cells, and other locations where restricted access is required. Being of narrow diameter, and not largely affected by internal security grilles, this provides daylight to areas without providing electrical connections or escape access, and without allowing objects to be passed into a secure area.

Light pipes,{{Cite web |title=FAQ's {{!}} Light Pipes, PMI, PCB Assembly & More |url=https://vcclite.com/faqs/ |access-date=2025-05-26 |website=VCC |language=en-US}}{{Cite web |title=What are LED light pipes? |url=https://www.dialightsignalsandcomponents.com/what-are-led-light-pipes/ |access-date=2025-05-26 |website=www.dialightsignalsandcomponents.com}} as they are referred to in the electronics industry, are commonly used for directing light in electronic devices.

Configurations of light pipes can vary widely, from simple, consisting of pre-made rods cut to length, to highly complex custom molded or machined shapes. Light pipes are usually made from acrylic or polycarbonate optical fibers, or solid transparent acrylic or polycarbonate polymers. Sometimes other transparent plastics are used. The source of illumination, is from LEDs on a circuit board or other internal location, to indicator symbols or buttons on the exterior of the device’s enclosure.

Different colors of light can be displayed in several ways. Tinting the light pipe material, using a colored light pipe lens, or using a single color LED, are used to produce a permanent single color. Multiple colors can be displayed by using a clear light pipe with an RGB, RGBW, or RGBWW LED. Older designs have used two or more individual color LEDs routed from the indicator on the display panel to the same light pipe.

The configuration of these light pipes can vary greatly. Simpler light pipes designs may be made from a straight, cylindrical rod, or may be bent with multiple gentle curves preserving the smooth uniform shape of the cylinder walls. Alternatively a flexible optical fiber light pipe may be used. Complex designs of molded or machined configurations, commonly take on a highly elaborate shape that uses either gentle curving bends as in an optic fiber or has sharp prismatic folds which reflect off the angled corners. Multiple light pipes are often molded or machined from a single piece of plastic, permitting easy device assembly since the long thin light pipes are all part of a single rigid component that snaps into place.

Light pipe indicators make electronics cheaper to manufacture since the old way would be to mount a tiny lamp into a small socket directly behind the spot to be illuminated. This often requires extensive hand labor for installation and wiring. Light pipes permit all lights to be mounted on a single flat circuit board, but illumination can be directed up, and away from the board wherever it is required.

{{div col|small=no|colwidth=20em}}

• Anidolic lighting
• Daylighting
• Active daylighting
• Passive daylighting
• Deck prism
• Green building
• Lighting
• Liter of Light project
• Over illumination
• Passive house
• Passive solar building design
• Remote Skylights
• Prism glass
• Tubeless skylight
• Solar power, esp. the sections on solar lighting and solar design in architecture
• Zero-energy building
• Resonator

{{div col end}}

{{reflist|30em}}

{{external links|date=March 2021}}

{{Commons category|Tubular daylighting devices}}

• [https://www.corning.com/worldwide/en/products/advanced-optics/product-materials/specialty-fiber/light-diffusing-fiber2.html Corning Fibrance Light-Diffusing Fiber]
• Light Tubes on "Potsdamer Platz" are made by Heliobus AG Switzerland [http://www.heliobus.com]
• [https://web.archive.org/web/20051121153123/http://www.smarthouse.duke.edu/downloads/smart_lighting_noor.ppt Smart Lighting for a Smart House Study ( PowerPoint Presentation ) ]
• [https://web.archive.org/web/20060713082109/http://www.fsec.ucf.edu/bldg/active/fenestration/solLighting/index.htm Solar lighting] and [https://web.archive.org/web/20060914085105/http://www.fsec.ucf.edu/bldg/active/fenestration/solLighting/piped.htm Illumination of Buildings using Light Pipes], Florida Solar Energy Center (at the University of Central Florida)
• [https://web.archive.org/web/20060405112728/http://etheses.nottingham.ac.uk/archive/00000026/01/Thesis_-_Joel_Callow.pdf Daylighting Using Tubular Light Guide Systems] (thesis)
• {{in lang|de}} an overview over light guidance – [http://bine.info/pdf/infoplus/pro0100systematik.pdf PDF], [https://web.archive.org/web/20110721185632/http://bine.info/pdf/infoplus/pro0100systematik.pdf HTML]
• [https://web.archive.org/web/20030517023353/http://www.iaeel.org/iaeel/archive/right_light_proceedings/Proceedings_body/BOK4/RL4shao.pdf "A Study of Performance of Light Pipes Under Cloudy and Sunny Conditions in the UK"]
• [https://web.archive.org/web/20050328022348/http://www.world-science.net/othernews/050310_suntubefrm.htm Wayback Archive of; "Sunlight in a tube", World Science, 2005]
• A series of [https://web.archive.org/web/20090522111628/http://www.sunpipe.co.uk/technical/index.php technical reference] information pages from the UK, referring to installation and mounting information
• [https://web.archive.org/web/20060907234851/http://ncr101.montana.edu/Light1994Conf/6_6_Kneipp/Kneipp%20text.htm "Use of prismatic films to control light distribution", K. G. Kneipp, International Lighting in Controlled Environments Workshop, T.W.Tibbitts (editor), 1994, NASA-CP-95-3309] (with an overview on the piping of light)
• {{in lang|de}} Alexander Rosemann: Hohllichtleiter für Tageslichtnutzung. Pflaum Verlag, München 2002. {{ISBN|3-7905-0862-4}}
• {{citation|doi=10.1016/j.enbuild.2004.09.014|title=A design tool for predicting the performances of light pipes|journal=Energy and Buildings|volume=37|issue=5|pages=485|year=2005|last1=Jenkins|first1=David|last2=Muneer|first2=Tariq|last3=Kubie|first3=Jorge|bibcode=2005EneBu..37..485J }}
• UK based [https://web.archive.org/web/20090308090727/http://www.sunpipe.co.uk/sunpipe/index.php Monodraught SunPipe] (and www.sunpipe.info) with extensive technical and reference information
• UK based and www.glidevail.com with extensive technical and reference information
• [https://demos.smu.ca/demos/optics/66-water-lightguide Using Water as a Light Tube]

• [http://blog.modernmechanix.com/2006/06/01/depthscrapers-defy-earthquakes/#more-715 the Japanese approach of "depthscraper"] {{Webarchive|url=https://web.archive.org/web/20120411190451/http://blog.modernmechanix.com/2006/06/01/depthscrapers-defy-earthquakes/#more-715 |date=2012-04-11 }} : a rotating mirror planned to throw sunlight deep down into a courtyard.
• Courtyard facade with heliostats in Karl-Scharnagl-Ring Street in Munich, Germany – [http://www.learn.londonmet.ac.uk/packages/synthlight/handbook/doc/cs3_munich.pdf PDF], [https://web.archive.org/web/20061014224726/http://www.learn.londonmet.ac.uk/packages/synthlight/handbook/doc/cs3_munich.pdf HTML]
• [https://web.archive.org/web/20060908070032/http://www.tribecatrib.com/newsjune05/mirrors.htm Heliostats in New York City, USA]
• Description, among other topics, of the [https://web.archive.org/web/20060907234851/http://ncr101.montana.edu/Light1994Conf/6_6_Kneipp/Kneipp%20text.htm 3M Solar Optical Products Daylighting Panel]
• [http://v3.espacenet.com/searchResults?locale=en_EP&EC=F21S11%2F00&ST=advanced&compact=false&DB=EPODOC Listing of patent publications] within the [http://www.uspto.gov/web/patents/classification/cpc/html/defF21S.html#F21S11/00 CPC class F21S11/00] ("Lighting devices or systems using daylight"), some of which relate to light tubes, for example:
• [http://www.freepatentsonline.com/4761716.html US patent 4761716]
• [http://www.freepatentsonline.com/6502950.html US patent 6502950]
• [http://www.freepatentsonline.com/6502950.html US patent 6840645]

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