Projected image from a video projector in a home cinema. Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home

A video projector takes a video signal and projects the corresponding image on a projection screen using a lens system. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images In Telecommunication, signalling (UK spelling or signaling (US spelling has the following meanings The use of signals for controlling communications Projection screens are installations consisting of blank surface and a support structure used for displaying a projected Image for the view of an audience A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging 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 conference room presentations, classroom training, and home theatre applications. Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home

Overview

A video projector may also be built into a cabinet with a rear-projection screen (rear-projection TV, or RPTV) to form a single unified display device, now popular for “home theater” applications. Rear projection is a type of large-screen Television display technology

Common display resolutions for a portable projector include SVGA (800×600 pixels), XGA (1024×768 pixels), 720p (1280×720 pixels), and 1080p (1920×1080 pixels). The display resolution of a Digital television or Computer display typically refers to the number of distinct pixels in each dimension that can be displayed Super Video Graphics Array or Ultra Video Graphics Array, almost always abbreviated to Super VGA, Ultra VGA or just SVGA or UVGA is In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image XGA, the Extended Graphics Array, is an IBM display standard introduced in 1990. 720p is the shorthand name for a category of HDTV video modes

The cost of a device is not only determined by its resolution, but also by its light output, acoustic noise output, contrast, and other characteristics. While most modern projectors provide sufficient light for a small screen at night or under controlled lighting such as in a basement with no windows^[1], a projector with a higher light output (measured in lumens, abbreviated “lm”) is required for a larger screen or a room with a higher amount of ambient light. In photometry, luminous flux or luminous power is the measure of the perceived power of Light. The lumen (symbol lm) is the SI unit of Luminous flux, a measure of the perceived power of Light. A rating of 1500 to 2500 ANSI lumens or lower is suitable for smaller screens with controlled lighting or low ambient light. ^[1][2] Between 2500 and 4000 lm is suitable for medium-sized screens with some ambient light or dimmed light. Over 3000 lm is appropriate for very large screens in a large room with no lighting control (for example, a conference room). Projected image size is important; because the total amount of light does not change, as size increases, brightness decreases. Image sizes are typically measured in linear terms, diagonally, obscuring the fact that larger images require much more light (proportional to the image area, not just the length of a side). Increasing the diagonal measure of the image by 25 % reduces the image brightness by 35 %; an increase of 41 % reduces brightness by half.

Projection technologies

• CRT projector using cathode ray tubes. A CRT projector is a Video projector that uses a small high-brightness CRT (or picture tube as the image generating element The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or This typically involves a blue, a green, and a red tube. Minimal maintenance is required (unlike projectors that use expensive lamps which must be periodically replaced after they burn out). This is the oldest system and 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
• LCD projector using LCD light gates. An LCD projector is a type of Video projector for displaying video images or computer data on a screen or other flat surface 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, although recent advances have minimized this.
• DLP projector using Texas Instruments’ DLP technology. Digital Light Processing (DLP is a Trademark owned by Texas Instruments, representing a technology used in projectors and Video projectors It was Texas Instruments ( better known in the electronics industry (and popularly as TI, is an American company based in Dallas, Texas, USA Digital Light Processing (DLP is a Trademark owned by Texas Instruments, representing a technology used in projectors and Video projectors It was This uses one, two, or three microfabricated light valves called digital micromirror devices (DMDs). Microfabrication or micromanufacturing are the terms to describe processes of fabrication of miniature structures of Micrometre sizes and smaller A Digital Micromirror Device, or DMD is an Optical Semiconductor that is the core of DLP projection Technology, and was 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 simultaneously. Primary colors are sets of Colors that can be combined to make a useful range ( Gamut) of colors
• LCOS projector using Liquid crystal on silicon. Liquid crystal on silicon ( LCOS or LCoS) is a "micro-projection" or "micro-display" Technology typically applied in projection Liquid crystal on silicon ( LCOS or LCoS) is a "micro-projection" or "micro-display" Technology typically applied in projection
• D-ILA JVC’s Direct-drive Image Light Amplifier based on LCOS technology. Liquid crystal on silicon ( LCOS or LCoS) is a "micro-projection" or "micro-display" Technology typically applied in projection
• LED Use an array of Light Emmitting Diodes as the light source, negating the need for lamp replacement.

Obsolete technologies

• Eidophor oil-film projectors
• Talaria oil-film projectors
• ILA (Light Image Amplifier) light valves
• Schmidt-CRT, developed by Kloss Video

DIY video projectors

With a growing DIY-community and an increasing interest in low cost devices, some hobbyists have endeavored to build their own projectors from kits, sourced components, or from scratch. An Eidophor was a Television projector used to create theater-sized images Taleria was the brand name of a large-venue Video projector from General Electric. The Schmidt-Cassegrain is a Catadioptric Telescope. It combines a folded optical path with a corrector plate to make a compact astronomical instrument The Kloss Video Corporation is a company founded in 1977 by noted engineer Henry Kloss in to develop and market high-performance video projection systems No-frills or no frills is a term used to describe any service or product for which the non-essential features have been removed A hobby is a spare-time Recreational pursuit Etymology A Hobby horse is a wooden or Wickerwork toy made to be Through the internet, the community is now able to obtain plans to construct DIY-video projectors. ^{[3] [4]} and there is a growing trend toward building them for domestic requirements and classroom use. Rm46jpg|thumb|Classroom in St Eunan's College, Letterkenny, Ireland]] A classroom is a Room in which Teaching or Learning activities The DIY-projectors are now being used both in developed countries and in developing countries in the interest of providing education as well as for entertainment purposes. Developing countries are countries that haven't reached Western-style standards of democratic government free market economy industrialization social programs and human rights guaranties Education encompasses both the Teaching and Learning of Knowledge, proper conduct, and technical competency See also Entertainment (disambiguation and The Entertainer (disambiguation Entertainment is an activity designed to give people

See also

• Large-screen television technology
• Projector for a directory of projector types
• Handheld projector
• Projection screen
• Screen door effect
• Digital divide
• Comparison of display technology
• Digital cinema

Major manufacturers

• 3M
• Barco (www.barco.com)
• BenQ
• Christie
• Digital Projection International
• EIKI
• Epson
• Hitachi, Ltd.
• InFocus
• Kloss Video (defunct)
• Lenovo
• Lumens
• Matsushita (Panasonic)
• Mitsubishi
• NEC
• Optoma
• Panasonic
• Samsung
• Sharp
• Sony
• Sanyo
• Texas Instruments (component supplier of DLP technology)
• Toshiba
• Viewsonic

References