![Projection-screen-home2](https://upload.wikimedia.org/wikipedia/commons/6/6c/Projection-screen-home2.jpg)
A video projector is an
image projector
A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer types ...
that receives a
video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
and projects the corresponding image on a
projection screen
A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed, as in a movie theater; painted on the ...
using a
lens
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
system. Video projectors use a very bright
ultra-high-performance lamp
An ultra-high-performance lamp, often known by the Philips trademark UHP, is a high-pressure mercury arc lamp. These were originally known as ultra-high-pressure lamps, because the internal pressure can rise to as much as 200 atmospheres when the ...
(a special
mercury arc lamp
A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz
Fused quartz, fused silica or quartz glass is a glass consi ...
), Xenon arc lamp,
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
or solid state blue, RB, RGB or remote fiber optic RGB
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
s to provide the illumination required to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. 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. Projectors using RB lasers use a blue laser with a phosphor wheel in conjunction with a conventional solid state red laser.
Video projectors are used for many applications such as conference room presentations, classroom training,
home cinema
Home cinema, also called home theaters or theater rooms, are home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a roo ...
, movie theaters and
concerts
A concert is a live music performance in front of an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, choir, or musical band, band. Concerts are held in a w ...
, having mostly replaced
overhead,
slide
Slide or Slides may refer to:
Places
* Slide, California, former name of Fortuna, California
Arts, entertainment, and media Music Albums
* ''Slide'' (Lisa Germano album), 1998
* ''Slide'' (George Clanton album), 2018
*''Slide'', by Patrick Glees ...
and conventional
film projector
A movie projector is an opto-mechanical device for displaying motion picture film by projecting it onto a screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras. Moder ...
s. In schools and other educational settings, they are sometimes connected to an
interactive whiteboard
An interactive whiteboard (IWB), also known as interactive board or smart board, is a large interactive display board in the form factor of a whiteboard. It can either be a standalone touchscreen computer used independently to perform tasks ...
. In the late 20th century they became commonplace in
home cinema
Home cinema, also called home theaters or theater rooms, are home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a roo ...
. Although large
LCD television
Liquid-crystal-display televisions (LCD TVs) are television sets that use liquid-crystal displays to produce images. They are, by far, the most widely produced and sold television display type. LCD TVs are thin and light, but have some disadvantag ...
screens became quite popular, video projectors are still common among many home theater enthusiasts.
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 screen to form a single unified display device.
Common
display resolution
The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is ...
s include
SVGA
Super VGA (SVGA) is a broad term that covers a wide range of computer display standards that extended IBM's VGA
Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the I ...
(800×600
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the smal ...
s),
XGA (1024×768 pixels), SXGA+ (1400x1050 pixels),
720p
720p (1280×720 px; also called HD ready, standard HD or just HD) is a progressive HDTV signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcast ...
(1280×720 pixels), and
1080p
1080p (1920×1080 progressively displayed pixels; also known as Full HD or FHD, and BT.709) is a set of HDTV high-definition video modes characterized by 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen vert ...
(1920×1080 pixels), 4K UHD (3840x2160), as well as 16:10 aspect ratio resolutions including WXGA+ (1280x800 pixels) and WUXGA (1920x1200 pixels)
The cost of a projector is typically driven by its base technology, features, resolution, and light output. A projector with a higher
light output (measured in
lumens, “lm”) is required for a larger screen or for a room with a larger amount of ambient light. For example, a light output of approximately 1500 to 2500
ANSI
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
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 for 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 30,000 lm are used in large staging applications such as concerts, keynote addresses and displays projected on buildings.
A few
camcorder
A camcorder is a self-contained portable electronic device with video and recording as its primary function. It is typically equipped with an articulating screen mounted on the left side, a belt to facilitate holding on the right side, hot-swa ...
s have a
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
![kalht 01](https://upload.wikimedia.org/wikipedia/commons/e/ee/Kalht_01.jpg)
*
LCD projector
An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern equivalent of the slide projector or overhead projector. To display images, LCD (liquid-crystal display) ...
using
LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...
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” or pixelation effect, and the LCD panels deteriorating from heat & UV rays, leading to discolored spots or holes in the image, although recent advances have reduced the severity of these issues in some models.
*
DLP projector
Digital Light Processing (DLP) is a set of chipsets based on optical micro-electro-mechanical technology that uses a digital micromirror device. It was originally developed in 1987 by Larry Hornbeck of Texas Instruments. While the DLP imaging ...
using
Texas Instruments
Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globall ...
’
DLP technology. This uses one, two, or three
microfabricated light valve A light valve (LV) is a device for varying the quantity of light, from a source, which reaches a target. Examples of targets are computer screen surfaces, or a wall screen in the case of a light projector.
There are two basic principles of achievin ...
s called
digital micromirror device
The digital micromirror device, or DMD, is the microoptoelectromechanical system (MOEMS) that is the core of the trademarked DLP projection technology from Texas Instruments (TI). Texas Instrument's DMD was created by solid-state physicist and ...
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
A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows c ...
” which some people perceive when moving their eyes. More recent projectors with higher speed (2x or 4x) and otherwise optimised color wheels have lessened this effect. 3-chip DLP projectors do not have this problem, as they display each
primary color
A set (mathematics), set of primary colors or primary colours (see American and British English spelling differences#-our, -or, spelling differences) consists of colorants or colored lights that can be mixed in varying amounts to produce a gamu ...
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.
*LCoS projectors (
liquid crystal on silicon
Liquid crystal on silicon (LCoS or LCOS) is a miniaturized reflective active-matrix liquid-crystal display or "microdisplay" using a liquid crystal layer on top of a silicon backplane. It is also referred to as a spatial light modulator. LCoS w ...
). Such projectors often process light in the
Fourier domain
In physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time. Put simply, a time-domain graph shows how a signa ...
, which enables correction of optical aberrations using
Zernike polynomials
In mathematics, the Zernike polynomials are a sequence of polynomials that are orthogonal on the unit disk. Named after optical physicist Frits Zernike, winner of the 1953 Nobel Prize in Physics and the inventor of phase-contrast microscopy, th ...
. Some commercially available technologies include:
**
D-ILA
Liquid crystal on silicon (LCoS or LCOS) is a miniaturized reflective active-matrix liquid-crystal display or "microdisplay" using a liquid crystal layer on top of a silicon backplane. It is also referred to as a spatial light modulator. LCoS was ...
JVC’s Direct-drive Image Light Amplifier based on LCoS technology.
**
SXRD SXRD (Silicon X-tal Reflective Display) is Sony's proprietary variant of liquid crystal on silicon, a technology used mainly in projection televisions and video projectors. In the front and rear-projection television market, it competes directly wit ...
Sony’s proprietary variant of LCoS technology.
*
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
projectors use one of the above-mentioned technologies for image creation, with a difference that they use an array of Light Emitting Diodes as the light source, negating the need for lamp replacement.
*Hybrid
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
and
laser diode
file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a di ...
system developed by
Casio
is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It ...
. Uses a combination of Light Emitting Diodes and 445 nm
laser diode
file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a di ...
s as the light source, while image is processed with DLP (DMD) chip.
*
Laser diode
file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a di ...
projectors have been developed by
Microvision
The Microvision (aka Milton Bradley Microvision or MB Microvision) is the first Handheld console, handheld game console that used interchangeable ROM cartridge, cartridges and in that sense is reprogrammable. It was released by the Milton Bradley ...
and Aaxa Technologies. Microvision projectors use Microvision's patented
MEMS
Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...
laser beam-steering technology, whereas Aaxa Technologies uses laser diodes + LCoS.
*Laser projectors are now available from most projector manufacturers, including Barco, Canon, Christie Digital, Dell, Epson, Hitachi, NEC, Optoma, Panasonic, Sony, Viewsonic and many others. These units use a laser light source (instead of conventional lamps), and are used with most common projection technologies, including Single & 3-Chip DLP, LCD and LCoS. They offer numerous advantages, including eliminating the high cost and downtime of replacing lamps, variations in brightness and color that occur as lamps age and improved color fidelity. 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
A CRT projector is a video projector that uses a small, high-brightness cathode ray tube (CRT) as the image generating element. The image is then focused and enlarged onto a screen using a lens kept in front of the CRT face. The first color CRT ...
using
cathode ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms ( oscilloscope), pictu ...
s. Once dominated the 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
An Eidophor was a video projector used to create theater-sized images from an analog video signal. The name Eidophor is derived from the Greek word-roots ''eido'' and ''phor'' meaning 'image' and 'bearer' (carrier). Its basic technology was th ...
oil-film projectors
*LIA (
light image amplifier) light valves
*
Schmidt
Schmidt may refer to:
* Schmidt (surname), including list of people with the surname
* Schmidt (singer) (born 1990), German pop and jazz singer
* Schmidt (lunar crater), a small lunar impact crater
* Schmidt (Martian crater), a List of craters on ...
-CRT, developed by
Kloss Video
*
Talaria
The Talaria of Mercury ( la, tālāria or The Winged Sandals of Hermes grc, πτηνοπέδῑλος, or , ) are winged sandals, a symbol of the Greek messenger god Hermes (Roman equivalent Mercury). They were said to be made by the god Hepha ...
oil-film projectors
Do-it-yourself video projectors
Some
hobby
A hobby is considered to be a regular activity that is done for enjoyment, typically during one's leisure time. Hobbies include collecting themed items and objects, engaging in creative and artistic pursuits, playing Sport, sports, or pursu ...
ists build a do-it-yourself (
DIY
"Do it yourself" ("DIY") is the method of building, modifying, or repairing things by oneself without the direct aid of professionals or certified experts. Academic research has described DIY as behaviors where "individuals use raw and semi ...
) projector for
low cost. They build their projectors from kits, sourced components, or from scratch, using a television set as a light source. Through the internet, they obtain plans to construct them
for domestic and
classroom
A classroom or schoolroom is a learning space in which both children and adults learn. Classrooms are found in educational institutions of all kinds, ranging from preschools to universities, and may also be found in other places where education ...
use.
See also
*
3LCD
*
Comparison of display technology
This is a comparison of various properties of different display technologies.
General characteristics
Major technologies are CRT, LCD and its derivatives (Quantum dot display, LED backlit LCD, WLCD, OLCD), Plasma, and OLED and its derivati ...
*
Digital cinema
Digital cinema refers to adoption of digital technology within the film industry to distribute or project motion pictures as opposed to the historical use of reels of motion picture film, such as 35 mm film. Whereas film reels have to b ...
*
Digital divide
The digital divide is the unequal access to digital technology, including smartphones, tablets, laptops, and the internet. The digital divide creates a division and inequality around access to information and resources. In the Information Age in ...
*
Digital Light Processing
Digital Light Processing (DLP) is a set of chipsets based on optical micro-electro-mechanical technology that uses a digital micromirror device. It was originally developed in 1987 by Larry Hornbeck of Texas Instruments. While the DLP imaging ...
(DLP)
*
Handheld projector
A handheld projector (also known as a pocket projector, mobile projector, pico projector or mini beamer) is an image projector in a handheld device. It was developed as a computer display device for compact portable devices such as mobile ph ...
*
Inflatable movie screen
An inflatable movie screen is an inflatable framework with an attached projection screen. Inflatable screens are used for outdoor movies, film festivals, drive-in theaters, sports, social, fundraising and other events requiring outdoor projectio ...
*
Large-screen television technology
Large-screen television technology (colloquially big-screen TV) developed rapidly in the late 1990s and 2000s. Prior to the development of thin-screen technologies, rear-projection television was standard for larger displays, and jumbotron, a n ...
*
Live event support
Live event support includes staging, scenery, mechanicals, sound, lighting, video, special effects, transport, packaging, communications, costume and makeup for live performance events including theater, music, dance, and opera. They all share th ...
*
Projection screen
A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed, as in a movie theater; painted on the ...
*
Project Ariana
*
Projector (disambiguation)
A projector is a device that projects an image on a surface.
Projector may also refer to:
Computing
* Projector PSA, a software and cloud-computing company
* Projector, a version control system used in the Macintosh Programmer's Workshop
Weaponr ...
*
Screen door effect
The screen-door effect (SDE) is a visual artifact of displays, where the fine lines separating pixels (or subpixels) become visible in the displayed image. This can be seen in digital projector images and regular displays under magnification or a ...
*
Video designer
References
{{Authority control
Digital technology
Display devices
Home video
Office equipment
Projectors
Television terminology
Video hardware