LCD projector
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An LCD projector is a type of
Metal-halide lamps are used because they output an ideal color temperature and a broad spectrum of color. These lamps also have the ability to produce an extremely large amount of light within a small area; current projectors average about 2,000 to 15,000 American National Standards Institute (ANSI) lumens.
Other technologies, such as Digital Light Processing (DLP) and liquid crystal on silicon (LCOS) are also becoming more popular in modestly priced video projection.
Projection surfaces
Because they use small lamps and the ability to project an image on any flat surface, LCD projectors tend to be smaller and more portable than some other types of projection systems. Even so, the best image quality is found using a blank white, grey, or black[citation needed] (which blocks reflected ambient light) surface, so dedicated projection screens are often used.
Perceived color in a projected image is a factor of both projection surface and projector quality. Since white is more of a neutral color, white surfaces are best suited for natural color tones; as such, white projection surfaces are more common in most business and school presentation environments.
However, darkest black in a projected image is dependent on how dark the screen is. Because of this, some presenters and presentation-space planners prefer gray screens, which create higher-perceived contrast. The trade-off is that darker backgrounds can throw off color tones. Color problems can sometimes be adjusted through the projector settings, but may not be as accurate as they would on a white background.
Throw ratio
A projector's throw ratio is used when installing projectors to control the size of the projected display.[1] For example, if the throw ratio is 2:1 and the projector is fourteen feet away from the screen, then the display width will be seven feet.
History
Early experiments with liquid crystals to generate a video image were done by John A. van Raalte at the RCA-Laboratories in 1968.[2] His concept was based on e-beam-addressing to generate an electronic charge pattern corresponding to a video image, which in turn controlled the LC layer of a reflective LC cell. E-beam-addressing requires a CRT with a modified faceplate to generate a charge pattern on its surface. No practical application of this concept for projection purposes is known. However, a similar concept was used for print heads without an LCD.
The first experiments with a direct-driven, transmissive matrix-addressed LCD using a converted slide projector by
A lot of effort went into optimizing thin-film transistors (TFT) suitable for
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Gene Dolgoff had the idea of using LCDs as light valves in projectors. However, he had to wait until 1984 to get a digitally-addressable LCD matrix device with sufficient resolution and contrast, which is when he completed building his LCD video projector. After building it, he saw many problems that had to be corrected including major light losses and very noticeable pixels (sometimes referred to as the "screen-door effect"). He then invented new optical methods to create efficient and bright projectors and invented depixelization to reduce the screen-door effect.
At about the same time, the German company "Bonner Ingenieurbüro für Optoelektronik CrystalVision" started experimenting with LCD projection devices from 1985 onwards. Although traditional slide projectors already used
With patents filed worldwide (filing his first LCD video projector patent application in 1987), Dolgoff started Projectavision, Inc. in 1988, as one of the world's first dedicated LCD-projector companies, which he took public on Nasdaq in 1990. He licensed the technology to other companies including Panasonic and Samsung. Early pioneers of LCD projection in Japan were Epson and Sharp,[8] which launched their own color video projector products in 1989.
In 1989, Projectavision, Inc. was awarded the first
Since 2005,[10] the only remaining manufacturers of the LCDs for LCD projectors are Japanese imaging companies Epson and Sony. Epson owns the technology and has branded it as "3LCD". To market 3LCD projector technology, Epson also set up a consortium called the "3LCD Group" in 2005 with other projector manufacturer licensees of 3LCD technology that use it in their projector models.
Early LCD systems were used with existing overhead projectors. The LCD system did not have a light source of its own: it was built on a large "plate" that sat on top of the projector in place of transparencies. This provided a stop-gap solution in the era when the computer was not yet a universal display medium, creating a market for LCD projectors before their current main use became popular.
This technology was employed in some sizes of rear-projection television consoles when there was a cost advantages in mid-size sets (40- to 50-inch diagonal). In 2014, 60-inch 1080p flat panel televisions were less costly than a projector with 1080p native resolution. Projection systems were typically marketed as offering a diagonal image size of 100 to 300 inches.
In 2004 and 2005, LCD front projection began a comeback with the introduction of the dynamic iris and other modifications that have improved perceived contrast to levels similar to DLP.
The basic design of an LCD projector is frequently used by hobbyists who build their own DIY (do-it-yourself) projection systems. The basic technique is to combine a high color-rendering index (CRI) high-intensity discharge lamp (HID lamp) and ballast with a condenser and collector Fresnel lens, an LCD removed from a common computer display and a triplet lens.
See also
References
- ^ "Throw Ratios and Viewing Distances". Archived from the original on 2013-02-04. Retrieved 2009-03-18. Throw
- ^ J.A. van Raalte, Reflective liquid crystal television display, Proc. IEEE, Vol. 56, No. 12, pp. 2146–2149
- ^ P.J. Wild, Matrix-addressed liquid crystal projection display, Digest of Technical Papers, International Symposium, Society for Information Display, June 1972, pp. 62–63
- ^ Slide sandwiched to liquid crystal gives variable display. Electronics, May 8, 1972, p. 78
- ^ U.S. patent 3,895,866: Alfred de Quervain, Peter Wild, Information-bearing Devices and Projection Display Systems therefor, filed Nov. 29, 1972
- ^ U.S. patent 4,952,925: Bernt Haastert, Projectable passive liquid-crystal flat screen information centers, filed Jan. 25, 1988
- ^ TV-Kino für jedermann. In: Funk + Fernseh Journal, No. 7, July 1989, p. 8.
- ^ [1]| Hornbeck, TI: From cathode rays to digital micromirrors:A history of electronic projection display technology
- ^ "Audiovisual Systems – Electronic Projection – Fixed Resolution Projectors (Retired 25 July 2003)". ANSI/NAPM. Retrieved 28 November 2022.
- ^ "Leading Projector Manufacturers Fujitsu, Hitachi, Panasonic, Sanyo and Sony Join Forces with Epson to Educate the Market about Benefits of Three-Panel Liquid Crystal Display Technology – Projectors Press Releases – Epson Australia". epson.com.au. Epson. Retrieved 9 October 2021.
- Powell, Evan (2002). "Epson's 730c: Best of Class in 2000-Lumen Portables", projectorcentral.com
- Business Wire (2005). "Leading Projector Manufacturers Fujitsu, Hitachi, Panasonic, Sanyo and Sony Join Forces with Epson to Educate the Market about
Benefits of Three-Panel, Liquid Crystal Display Technology", projectorcentral.com
- Lawler, Richard (2006). "LG's 100-inch LCD set for mass production", Engadget
- Breeden, John (2009). "LCD monitors go big, with mostly good results", GCN, p. 3
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- Throw Ratio – article on projector throw and display size ratios.
- DLP vs LCD projectors guide – how do LCD and DLP projectors work and what are their advantages and disadvantages
- LCD projectors vs DLP projectors – easy guide on LCD and DLP technology in projectors and how they compare
- Which is Better DLP or LCD Projector – which is better DLP or LCD projector
- 3LCD Projector Technology
- Projector Power – Article on how much power LCD projector consumes
Further reading
- Fischetti, Mark (November 2007). "Two Technologies Shine". Scientific American. pp. 110–111.
Two technologies – micromirrors and liquid-crystal displays (LCDs) – have been vying for these markets, but they are doing equally well in today's home and business areas....