how does a rear projection tv work?

Question

how does a Rear Projection tv work. is there a projecter like one of those boxs that projects on to the screen like at the movie theater. or is it just like a reqular tv like a flat screen.

i will be giving out 10 points to the best answer

Answer 1

A rear projection television (or RPTV as it’s often known in the consumer electronics world) is a specific type of rear projection display system the latter of which may be classified into two primary categories based on their principle of operation: transmissive and reflective. Reflective RP systems can be further subdivided into single-mirror and dual-mirror systems.

Purely transmissive rear projection systems are very rare in residential applications. Most rear projection display systems, including RPTVs, that are designed for residential use, utilize a mirror structure which comprises part of a chassis often enclosed by an outer cabinet.

A reflective display system consists of an internally mounted projector (or projection ‘engine,’ not unlike that of the typical front projector,) one or two mirrors (preferably of the first-surface variety,) a transmissive display screen (either optical diffusion or the much more common Fresnel-Lenticular type,) and some form of an outer enclosure. Projectors used in RPTVs function no different than projectors used in front projection applications (other than the image is reversed) and are available in any of the standard projection display technologies, such as CRT, LCD, LCoS, or DLP, with which you may already be familiar.

Though there are many variations when it comes to specifics on RPTV construction, in general a video signal is input to an internal projector where the video image is produced and magnified by a set of lenses. From the projector the image is then focused onto a mirror assembly consisting of one or two mirrors, which in turn magnify and reflect the video image onto the back of a large transmissive display screen fastened to the front of the RPTV’s chassis.

In addition to the task of image magnification the mirrors are also used to ‘fold the light path’ thereby greatly reducing the overall depth of the enclosure. However, in the real world mirrors are not perfect reflectors though some mirrors are better than others. The best reflectivity that a person could expect in a high performance rear-projection display system is typically no more than 94% (and on very rare occasion 97%) per mirror; so each mirror that is used will effectively reduce the efficiency of the overall optical subsystem. This is one area where a purely transmissive system has the advantage over a reflective system.

Among a variety of factors, including the need to counter multiple and/or lower quality mirrors, as well as lower powered projectors, manufacturers of RPTV systems will invariably resort to the use of Fresnel-Lenticular screen technology to optically boost the light output of the their RPTVs. A Fresnel-Lenticular screen has several undesirable characteristics when compared to a quality optical diffusion screen but is often necessary when using an RPTV in a viewing environment where a high quantity of ambient light may be present.

To get a better idea of what I’ve described above please have a look at the following documents and pictures.

http://electronics.howstuffworks.com/projection-tv.htm

http://www.da-lite.com/education/angles_of_view.php?action=details&issueid=28
http://www.da-lite.com/education/angles_of_view.php?action=details&issueid=36
http://www.da-lite.com/products/product.php?cID=10&pID=241

http://www.draperinc.com/images/RearScreen/Images/RpxComplete.jpg
http://www.draperinc.com/images/RearScreen/Images/RPX.jpg
http://www.draperinc.com/images/RearScreen/Images/RPXPrecision.jpg
http://www.draperinc.com/images/RearScreen/instructions/RPX_Inst.pdf
http://www.draperinc.com/images/2007Catalogs/VisualPresentation/VPP07_2007Catalog%2038.pdf

http://www.stewartfilmscreen.com/mirrorproducts.html
http://www.stewartfilmscreen.com/spec_sheets/opta.pdf
http://www.stewartfilmscreen.com/spec_sheets/mvpsl_spec.pdf
http://www.stewartfilm.com.cn/001/business_professional_4-2.html
 

Answer 2

Rear Projection Mirror System

Answer 3

Modern DLP and LCD rear-projectors work very similar to the movie theater projectors. A light-bulb shines onto a color wheel or LCD panels that contain the actual movie. The light is reflected onto the back of a plastic screen and you watch from the front.

However: the old-style "Big Screen" televisions work a bit different. They have 3 CRT tubes (like a old TV tube), but each of these tubes are dedicated to a different color. The 3 tubes (called "Guns") focus onto a mirror that then reflects the image onto the back of a plastic screen.

Answer 4

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It's sounds like your projection tube is getting close to failing. As the life of the tube wears out the picture will get darker. It will cost about $200-$300 for the tube. I don't know what the labor would be. You need to contact the service department of the store you bought it from and ask them. Have the Brand and model number handy.