Editing Video projector

{{Short description|Device that projects video onto a surface}}
{{Hatnote|This article is about home and business projectors; for video projectors used in movie theaters, see [[digital cinema]].}}

[[File:Projektor PGD2870W firmy Sharp.jpg|thumb|A projector in a standard form factor: The PG-D2870 projector from [[Sharp Corporation|Sharp]], which uses [[digital light processing]] technology]]
[[File:Projection-screen-home2.jpg|thumb|An image from a video projector in a [[home cinema]]]]

A '''video projector''' is an [[image projector]] that receives a [[video signal]] and projects the corresponding image onto a [[projection screen]] using a [[lens (optics)|lens]] system. [[Video]] projectors use a very bright [[ultra-high-performance lamp]] (a special [[mercury arc lamp]]), [[Xenon arc lamp]], [[Metal-halide lamp|metal halide lamp]], [[LED]] or solid state blue, RB, [[RGB color model|RGB]] or [[fiber-optic]] [[laser]]s to provide the illumination required to project the image. Most modern projectors can correct any curves, blurriness and other inconsistencies through manual settings.

Video projectors are used for many applications such as conference room [[presentation]]s, classroom training, [[home cinema]], [[movie theater]]s, and [[concerts]], having mostly replaced [[overhead projector|overhead]], [[slide projector|slide]] and conventional [[Movie projector|film projector]]s. In schools and other educational settings,<ref>{{cite web|title=Christmas is a time for taking -- from schools |url=https://www.latimes.com/archives/la-xpm-2007-jan-18-me-theft18-story.html|work=[[Los Angeles Times]]|author=Charles Proctor|date=January 18, 2007|access-date=2010-11-26}}</ref> they are sometimes connected to an [[interactive whiteboard]]. In the late 20th century, they became commonplace in home cinema. Although large [[LCD television]] screens became quite popular, video projectors are still common among many home theater enthusiasts. In some applications, video projectors have been replaced with large monitors or LED screens,<ref>{{Cite web |title=Interactive whiteboard projectors fading from classrooms |url=https://www.toledoblade.com/local/education/2022/06/11/educational-technology-smartboard-trend-losing-traction/stories/20220611123 |access-date=2024-08-01 |website=The Blade |language=en}}</ref> or their replacement has been explored.<ref>{{Cite web |date=2023-11-27 |title=LG and Odeon Multicines Open World’s First 100% LED Cinema with Dolby Atmos in Madrid - Boxoffice |url=https://www.boxofficepro.com/lg-odeon-multicines-open-worlds-first-100-percent-led-cinema-dolby-atmos-madrid/ |access-date=2024-08-01 |website=www.boxofficepro.com |language=en-US}}</ref><ref>{{Cite web |last=Giardina |first=Carolyn |date=2023-04-15 |title=LED Screens for Theaters: Is the Buzzy Tech Worth the Cost? |url=https://www.hollywoodreporter.com/business/digital/led-screens-samsung-sony-lg-1235374322/ |access-date=2024-08-01 |website=The Hollywood Reporter |language=en-US}}</ref><ref>{{Cite web |last= |first= |title=‘Word-first’ acoustic transparent LED cinema screen debuts |url=https://www.avinteractive.com/news/displays/word-first-acoustic-transparent-led-cinema-screen-debuts-03-07-2024/ |access-date=2024-08-01 |website=AV Magazine |language=en}}</ref>

==Overview==
A video projector, also known as a digital projector, may project onto a traditional reflective projection screen, or it may be built into a cabinet with a translucent [[rear-projection television|rear-projection screen]] to form a single unified display device.

Common [[display resolution]]s  include [[SVGA]] (800×600 [[pixel]]s), [[XGA]] (1024×768 pixels), SXGA+ (1400×1050 pixels), [[720p]] (1280×720 pixels), and [[1080p]] (1920×1080 pixels), 4K UHD (3840×2160), as well as 16:10 aspect ratio resolutions including WXGA+ (1280×800 pixels) and WUXGA (1920×1200 pixels).

If a blue laser is used, a phosphor wheel is used to turn blue light into white light, which is also the case with white LEDs. (White LEDs do not use lasers.) A wheel is used in order to prolong the lifespan of the phosphor, as it is degraded by the heat generated by the laser diode. Remote fiber-optic RGB laser racks can be placed far away from the projector, and several racks can be housed in a single, central room. Each projector can use up to two racks, and several monochrome lasers are mounted on each rack, the light of which is mixed and transmitted to the projector booth using optical fibers.<ref>{{cite web |title=Christie 6P laser lights CGV’s biggest screen in South Korea |url=https://www.etnow.com/news/2015/10/christie-6p-laser-lights-cgvs-biggest-screen-in-south-korea |access-date=2023-12-28}}</ref><ref>{{cite web |title=Christie RGB laser projection |url=https://www.christiedigital.com/globalassets/resources/public/christie-rgb-laser-brochure.pdf |access-date=2023-12-28}}</ref><ref>{{cite web |title=Novel laser sources for large-venue projection markets |url=https://spie.org/news/1108-novel-laser-sources-for-large-venue-projection-markets?ArticleID=x24934&SSO=1}}</ref> Projectors using RB lasers use a blue laser with a phosphor wheel in conjunction with a conventional solid-state red laser.

The cost of a projector is typically driven by its base technology, features, resolution and light output. A projector with a higher [[luminous flux|light output]] (measured in [[lumen (unit)|lumens]]) is required for a larger screen or for a room with more ambient light.<ref>{{cite book|title=Automated Lighting: The Art and Science of Moving Light in Theatre, Live Performance, Broadcast, and Entertainment|url=https://books.google.com/books?id=zfu9727rvjgC&q=other+important+factors+are+the+contrast+ratio%2C+the+ambient+light&pg=PA344|author=Richard Cadena|year=2006|isbn=978-0-240-80703-4|publisher=[[Focal Press]]|pages=344}}</ref> For example, a light output of approximately 1500 to 2500 [[American National Standards Institute|ANSI]] lumens is suitable for small screens viewed in rooms with low ambient light; approximately 2500 to 4000 lm is suitable for medium-sized screens with some ambient light; over 4000 lm is needed for very large screens or use in rooms with no lighting control such as conference rooms. High brightness large-venue models are increasingly common in boardrooms, auditoriums and other high-profile spaces, and models up to 75,000 lm<ref>{{cite web | url=https://www.projectorcentral.com/Barco-Barco_XDL-4K75.htm | title=Barco XDL-4K75 DLP Projector }}</ref> are used in large staging applications such as concerts, keynote addresses and displays projected on buildings. Video projectors can have a mechanism similar to local backlight dimming to achieve higher contrast ratios by using 6 DLP chips: 3 for display, and 3 for local dimming.<ref>{{cite web | url=https://www.projectorcentral.com/Christie-names-home-theater-rep-for-Eclipse.htm | title=Christie to Sell Breakthrough Eclipse HDR Projector for Home Theaters }}</ref><ref>{{cite web | url=https://www.bigpicturebigsound.com/Best-Home-Theater-Projector-of-All-Time-Meet-The-Christie-Eclipse.shtml | title=Best Home Theater Projector of All Time? Meet the Christie Eclipse }}</ref>

A few [[camcorder]]s have a [[camcorder#Camcorder with built-in projector|built-in projector]] suitable to make a small projection; a few more powerful "pico projectors" are pocket-sized, and many projectors are portable.

==Projection technologies==
[[File:kalht 01.jpg|thumb|upright|A [[Zenith Electronics]] 1200 CRT-projector-based [[home theater]], ca. 2006]]
*[[LCD projector]] using [[LCD]] light gates. This is the simplest system, making it one of the most common and affordable for home theaters and business use. Common problems include a visible [[screen-door effect|screen-door or pixelation effect]], and the LCD panels deteriorating from heat and from [[Photo-oxidation of polymers|UV degradation]], leading to discolored spots or holes in the image, although recent advances have reduced the severity of these issues in some models.
*DLP projector using [[Texas Instruments]]’ [[digital light processing]] (DLP) technology. This uses one to three [[microfabrication|microfabricated]] [[light valve]]s called [[digital micromirror device]]s (DMDs). The single- and double-DMD versions use rotating color wheels in time with the mirror refreshes to modulate color. The most common problem with the single- or two-DMD varieties is a visible rainbow, which some people perceive when moving their eyes. More recent projectors with higher speed (2× or 4×) and otherwise optimized color wheels have lessened this effect. 3-chip DLP projectors do not have this problem, as they display each [[primary color]] simultaneously, and offer higher light output and more accurate color reproduction, however the cost is significantly higher and thus 3-chip DLP technology is typically used in large venue, high brightness models, as well as [[digital cinema]] projectors.
*[[liquid crystal on silicon]] (LCoS) projectors. Such projectors often process light in the [[Fourier optics|wavelength domain]], which enables correction of optical aberrations using [[Zernike polynomials]].<ref>{{Cite journal |doi = 10.1109/JDT.2015.2418436|title = Optimization-Based Adaptive Optical Correction for Holographic Projectors|journal = Journal of Display Technology|volume = 11|issue = 7|pages = 596–603|year = 2015|last1 = Kaczorowski|first1 = Andrzej|last2 = Gordon|first2 = George S.|last3 = Palani|first3 = Ananta|last4 = Czerniawski|first4 = Stanislaw|last5 = Wilkinson|first5 = Timothy D.|bibcode = 2015JDisT..11..596K|s2cid = 24142134}}</ref>  Some commercially available technologies include:
**[[D-ILA]] JVC’s Direct-drive Image Light Amplifier based on LCoS technology.
**[[SXRD]] Sony’s proprietary variant of LCoS technology.
*[[LED]] projectors use one of the above-mentioned technologies for image creation, with an array of [[light-emitting diode]]s (LEDs)as the light source, negating the need for lamp replacement.
*Hybrid [[LED]] and [[laser diode]] system developed by [[Casio]]. Uses a combination of LEDs and 445&nbsp;nm [[laser diode]]s as the light source, while image is processed with DLP chip.
*[[Laser diode]] projectors have been developed by Microvision and Aaxa Technologies. Microvision projectors use Microvision's patented [[Microelectromechanical systems|MEMS]] laser beam-steering technology, whereas Aaxa Technologies uses LCoS with [[laser diode]]s as the light source.
*Laser projectors use a monochrome blue laser light source to excite a yellow phosphor medium creating a broad spectrum light. This broadband spectrum light is then split into the primaries with a color wheel and are used with most common projection technologies, including single and 3-chip DLP, LCD and LCoS.<ref>{{Cite web |title=What's the difference between laser phosphor and RGB laser? |url=https://www.barco.com/na-en/inspiration/news-insights/2020-05-19-rgb-vs-laserphosphor |access-date=2023-06-24 |website=www.barco.com |language=en}}</ref> Typical laser light sources used in projectors are rated for 20,000 hours before the light output is reduced to 50%, whereas lamps lose brightness quickly and need to be replaced after as little as 1000–2000 hours.

===Obsolete technologies===
*[[CRT projector]] using [[cathode-ray tube]]s. Once dominated the video projection market, but given their limited light output, size, weight and need for complex alignment, they have since been displaced by digital projectors and are no longer being made.
*[[Eidophor]] oil-film projectors.
*LIA (light image amplifier) light valves.
*[[Liquid crystal on silicon#Technology|ILA]], marketed by Hughes-JVC. It is the predecessor to JVC's D-ILA offering.
*[[Schmidt-Cassegrain telescope|Schmidt]]-CRT, developed by [[Kloss Video Corporation|Kloss Video]].
*[[Talaria projector|Talaria]] oil-film projectors.

== Do-it-yourself video projectors ==
Some [[hobby]]ists build do-it-yourself ([[DIY]]) projectors at [[low cost]]s. They build their projectors from kits, sourced components, or from scratch, using a television set, cellphone screen, or LED lighting as a light source.<ref>{{cite web |last1=DIY Perks |title=Building a TRUE 4k home cinema projector |url=https://www.youtube.com/watch?v=YfvTjQ9MCwY&t=1519s |website=Youtube |access-date=23 August 2023}}</ref> DIY construction plans can be obtained through the internet<ref>{{cite web |author=Völkel |first=Frank |date=November 14, 2004 |title=Supersize Your TV for $300: Build Your Own XGA Projector! |url=https://www.tomshardware.com/reviews/supersize-tv,918.html |url-status=live |archive-url=https://web.archive.org/web/20101229155255/http://www.tomsguide.com/us/supersize-your-tv-for,review-342.html |archive-date=2010-12-29 |access-date=2022-12-27 |publisher=[[Tom's Hardware]]}}</ref> for domestic and [[classroom]] use.

==See also==
*[[3LCD]]
*[[Comparison of display technology]]
*[[Digital cinema]]
*[[Digital divide]]
*[[Handheld projector]]
*[[Holographic screen]]
*[[Inflatable movie screen]]
*[[Large-screen television technology]]
*[[Live event support]]
*[[Projection mapping]]
*[[Projection screen]]
*[[Screen door effect]]
*[[Video designer]]

==References==
{{Commons category|Video projectors}}
{{Reflist}}

{{Display technology}}
{{Authority control}}

[[Category:Digital technology]]
[[Category:Electronic display devices]]
[[Category:Home video]]
[[Category:Office equipment]]
[[Category:Projectors]]
[[Category:Television terminology]]
[[Category:Video hardware]]