Video projector - AbsoluteAstronomy.com

A video projector is an image projector

Image projector

An image projector is an optical device that projects an image onto a surface, commonly a projection screen.Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers...

that receives a video

Video

Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...

signal and projects the corresponding image on a projection screen

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 wall; or semi-permanent or mobile, as in a conference room...

using a lens

Lens (optics)

A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...

system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for many applications such as, conference room presentations, classroom training, home theatre

Home cinema

Home cinema, also commonly called home theater, are home entertainment set-ups that seek to reproduce a movie theater experience and mood with the help of video and audio equipment in a private home....

and concerts. Projectors are widely used in many schools and other educational settings, sometimes connected to an interactive whiteboard

Interactive whiteboard

An interactive whiteboard , is a large interactive display that connects to a computer and projector. A projector projects the computer's desktop onto the board's surface where users control the computer using a pen, finger, stylus, or other device...

to interactively teach pupils.

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

Rear-projection television

Rear-projection television or RPTV is a type of large-screen television display technology. Up until the mid-2000s, most of the relatively affordable consumer large screen TVs up to used rear-projection technology...

to form a single unified display device.

Common display resolution

Display resolution

The display resolution of a digital television 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 controlled by all different factors in cathode ray tube , flat panel or projection...

s for a portable projector include SVGA (800×600 pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

s), XGA (1024×768 pixels), 720p

720p

720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan...

(1280×720 pixels), and 1080p

1080p

1080p is the shorthand identification for a set of HDTV high-definition video modes that are characterized by 1080 horizontal lines of resolution and progressive scan, meaning the image is not interlaced as is the case with the 1080i display standard....

(1920×1080 pixels).

The cost of a device is determined not only by its resolution but also by its light output. A projector with a higher light output

Luminous flux

In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of...

(measured in lumens

Lumen (unit)

The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...

, “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

American National Standards Institute

The American National Standards Institute 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 organization also coordinates U.S. standards with international...

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.

A few camcorder

Camcorder

A camcorder is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage...

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

CRT projector
CRT projector
A CRT projector is a video projector that uses a small, high-brightness 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. Most modern CRT projectors are color and have three separate CRTs , and their own lenses to...

using cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

s. This typically involves a blue, a green, and a red tube. This is the oldest system still in regular use, but falling out of favor largely because of the bulky cabinet. However, it does provide the largest screen size for a given cost. This also covers three tube home models, which, while bulky, can be moved (but then usually require complex picture adjustments to get the three images to line up correctly).
LCD projector
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...

using LCD light gates. This is the simplest system, making it one of the most common and affordable for home theaters and business use. Its most common problem is a visible “screen door” or pixelation effect
Screen-door effect
The screen-door effect or fixed-pattern noise is a visual artifact of the projection technology used in digital projectors, where the fine lines separating the projector's pixels become visible in the projected image...

, although recent advances have reduced the severity of this effect.
DLP projector using Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

’ DLP technology. This uses one, two, or three microfabricated
Microfabrication
Microfabrication is the term that describes processes of fabrication of miniature structures, of micrometre sizes and smaller. Historically the earliest microfabrication processes were used for integrated circuit fabrication, also known as "semiconductor manufacturing" or "semiconductor device...

light valve
Light valve
A light valve 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....

s called digital micromirror device
Digital micromirror device
A digital micromirror device, or DMD, is an optical semiconductor that is the core of DLP projection technology, and was invented by Dr. Larry Hornbeck and Dr. William E. "Ed" Nelson of Texas Instruments in 1987....

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 (2x or 4x) and otherwise optimised color wheels have lessened this artifact. Systems with 3 DMDs never have this problem, as they display each primary color
Primary color
Primary colors are sets of colors that can be combined to make a useful range of colors. For human applications, three primary colors are usually used, since human color vision is trichromatic....

simultaneously.
LCoS projector
Liquid crystal on silicon
Liquid crystal on silicon is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. By way of comparison, LCD projectors use...

using Liquid crystal on silicon
Liquid crystal on silicon
Liquid crystal on silicon is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. By way of comparison, LCD projectors use...

.
- D-ILA JVC’s Direct-drive Image Light Amplifier based on LCoS technology.
- SXRD
  SXRD
  SXRD 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 with JVC's D-ILA and Texas Instruments' DLP...
  
  Sony’s proprietary variant of LCoS technology.
LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

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
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

and Laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

system developed by Casio
Casio
is a multinational electronic devices manufacturing company founded in 1946, with its headquarters in Shibuya, Tokyo, Japan. Casio is best known for its electronic products, such as calculators, audio equipment, PDAs, cameras, musical instruments, and watches...

. Uses a combination of Light Emitting Diodes and 445 nm laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

s as the light source, while image is processed with DLP (DMD) chip.
Laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

projectors have been developed by Microvision and Aaxa Technologies. Microvision laser projectors use Microvision's patented laser beam-steering technology, whereas Aaxa Technologies uses laser diodes + LCoS.

Obsolete technologies

Eidophor
Eidophor
An Eidophor was a television projector used to create theater-sized images. The name Eidophor is derived from the Greek word-roots ‘eido’ and ‘phor’ meaning 'image' and 'bearer'...

oil-film projectors
LIA (Light Image Amplifier) light valves
Schmidt
Schmidt-Cassegrain telescope
The Schmidt–Cassegrain is a catadioptric telescope that combines a cassegrain reflector's optical path with a Schmidt corrector plate to make a compact astronomical instrument that uses simple spherical surfaces.-Invention and design:...

-CRT, developed by Kloss Video
Talaria
Talaria projector
Talaria was the brand name of a large-venue video projector from General Electric.Light from a Xenon arc lamp was modulated by a light valve consisting of a rotating glass disc that was continuously re-coated with a viscous oil. An electron beam similar to the one in a cathode ray tube traced a...

oil-film projectors

Do-it-yourself video projectors

With a growing do-it-yourself (DIY) community and an increasing interest in low cost devices, some hobby

Hobby

A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...

ists have endeavored to build their own projectors from kits, sourced components, or from scratch. Through the internet, the community is now able to obtain plans to construct DIY-video projectors. There is a growing trend toward building them for domestic requirements and classroom

Classroom

A classroom is a room in which teaching or learning activities can take place. Classrooms are found in educational institutions of all kinds, including public and private schools, corporations, and religious and humanitarian organizations...

use. The DIY-projectors are now being used both in developed countries and in developing countries in the interest of providing education

Education

Education in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...

as well as for entertainment

Entertainment

Entertainment consists of any activity which provides a diversion or permits people to amuse themselves in their leisure time. Entertainment is generally passive, such as watching opera or a movie. Active forms of amusement, such as sports, are more often considered to be recreation...

purposes.

Overview

Projection technologies

Obsolete technologies

Do-it-yourself video projectors

See also