Rear Projection HDTVs - Rear Projection TV Technology Guide
Updated: December 13, 2012

Guide to Rear Projection HDTV Technology

Understanding the Pros and Cons of
Different Rear Projection TV Technologies

Today, sale of rear projection HDTVs represents just 2% of the big screen TV market, yet it is still the only TV display technology capable of delivering the biggest screen size for your money, this despite the fall in prices of large plasma and LED TVs and the latest drive by all major TV makers towards 70-inch+ LED TVs for the home entertainment market.

This HDTV guide discusses the only remaining rear projection TV technology in use today—DLP—versus other available rear projection technologies to get a better understanding of the advantages and limitations of each.

Mitsubishi WD-82840 3D-ready Internet-connected DLP TV
Mitsubishi WD-82840 3D DLP TV

For less than a 65-inch LED TV, this 82-inch DLP HDTV features 3D, Internet-TV, is ISFccc-ready for professional calibration, and includes a 16-speaker soundbar for one of the best sound experiences you will enjoy direct from the TV speakers.

DLP Rear Projection HDTVs: The only surviving RPTVs

Market analysts had long predicted the demise of rear projection HDTVs before they predicted the demise of plasma TV when Pioneer left the HDTV market in 2009. Yet plasma is still going strong and with rear projection, it was only on December 1, 2012 that Mitsubishi announced it will be discontinuing its present line of DLP HDTVs to focus on B-to-B and home theater video projectors.

It is true that in the process, the market for rear projection TVs shrunk to just under 2% of all large area displays sold in the US. Yet it remains a fact that Mitsubishi's announcement was a bit of disappointment as rear projection is still the only big screen TV technology that can deliver a massive size HDTV for a relatively inexpensive price tag in comparison to the latest massive LED TVs from Sharp.

OK, at this point, with Mitsubishi discontinuing its DLP line, rear projection HDTVs will soon disappear from major stores. In addition, many in the market for a massive screen TV solution may be somewhat weary opting for a DLP TV. Yet we believe that as long as these sets are available, there is no reason why one should refrain from opting for a DLP TV if this delivers the best option for your money. Mitsubishi will keep supporting its present product line of DLP rear prediction HDTVs; this has been promised, and this is the norm - that manufacturers keep supporting discontinued products for their whole designed lifetime.

In this HDTV guide, we discuss the pros and cons of DLP technology, the only rear projection TV technology in use today. We do not stop there; we also discuss other rear projection technologies that were still in use up to a few years ago to better bring about the advantages of the only surviving rear projection technology in the large area HDTV market.

Rear Projection Technologies Explained

Rear projection HDTV systems can be grouped under two main categories – those based on the old CRT tube, and microdisplay chips - namely rear projection systems based on DLP, LCD, and LCoS technologies. As stated earlier on, only DLP survived but only because the only rear projection TV maker left makes use of DLP.

CRT-based Rear Projection Systems

Up to a few years ago, the majority of RPTVs were tube-based systems using the traditional CRT to generate the picture image for projection onto a large screen. Relatively heavy and bulky by today standards, these box-type TVs were the first to disappear.

CRT-based systems Pros/Cons Summary list:




CRT RPTVs are relatively inexpensive.

Deliver well-saturated colors and better black levels than most microdisplay based RPTVs.

Once properly set up, top-level CRT RPTVs can deliver the best picture quality when viewed in a darkened environment.

Sets are bulky and extremely heavy.

Need regularly maintenance; CRT rear projection TVs are more prone to failure.

Images tend to be soft. It is only possible to enjoy the best picture after a lengthy and expensive professional calibration. Regular convergence adjustments are needed to maintain correct alignment of the red, green, and blue CRTs.

Image is not very bright and therefore not ideal for use in brightly lit rooms. 

Rear projection TVs using CRT-based display technology were the first to disappear - mainly because of their bulkier size.

Microdisplay Rear Projection Systems

Microdisplay-based rear projection HDTV sets use one or more (three - one for each primary color) microchips that contain hundreds of thousands of pixels to build up the image. Microdisplay rear projection technologies include DLP, LCD, and LCoS.

Contrary to CRT systems which depend on the light produced by the tube itself, microdisplay systems use an external light source, normally in the form of an HID lamp. This either bounces light off the microchip surface in the case of DLP and LCoS, or pass the light beam itself though the chip in the case of LCD to produce the image. This also explains why microdisplay-based rear projection HDTVs come with a substantially brighter picture than their CRT equivalents.

At the same time, the use of a lamp means that this has to be replaced regularly, typically every 3000 to 8000hrs, depending on the lamp technology, and equally important on the conditions of use; for example, too bright an image leads to a reduced lamp life. In most cases, lamp replacement can be done by the user, but this in itself brings about a typical expense of around $100 for each replacement lamp.

Some Samsung rear projection HDTVs made use of an LED light engine while Mitsubishi LaserVue uses a laser light engine with zero expected lamp replacements for the whole expected lifetime of the LaserVue.

Another distinct characteristic of microdisplay-based rear projection HDTVs is that these HDTV sets are substantially lighter and more compact than CRTs RPTVs.

Present-day designs of the latest microchip RPTVs, when viewed from the front- resemble more that of flat-panel plasma and LCD HDTVs rather than the big box look of traditional CRT RPTVs. However, you cannot wall-mount a rear projection HDTV as these have to sit on a suitable table stand to bring the rear projection HDTV screen at eye level.

DLP (Digital Light Processor) Rear Projection HDTVs:

Based on the Digital Micro-mirror Device, or DMD - originally developed by Texas Instruments, DLP rear projection has always been the most popular of all three microchip-based rear projection technologies, and as indicated earlier on, the only technology that survived so far.

Unlike LCD rear projection HDTVs, DLP-based 1080p HDTV sets use wobulation to produce a 1080p image from a 960x1080 pixel microchip. The whole process makes use of an optical actuator to offset (wobulate) the image by ½ pixel 120 times a second in the case of 1080p 60Hz HDTV, to create the 1920 pixels by 1080 lines 1080p 60Hz image.

This ½-pixel displacement also helps soften the pixel edges, leading to a seamless more film-like image with no visible pixel structure. In contrast, LCD based systems tend to break up in what is often referred to as ‘screen-door effect’ when viewing takes places at too close a distance especially with large display sizes.

Some tend to complain that wobulation leads to a too soft an image in comparison to other image technologies, but this is more a matter of personal taste.

Interesting here is this wobulation technique also gave rise to an interesting 3D TV technology - Checkerboard technology - that is capable of exceptionally very good 3D images on DLP HDTVs in comparison to what is possible with passive 3D glasses technology used on some LED TVs.

Traditional lamp-based DLP rear projection HDTVs have one major shortcoming. These sets use a spinning color wheel to create the red, green and blue primary color information necessary to build up the displayed image. The use of the color wheel makes these sets susceptible to what is known as the ‘rainbow effect’.

Some people can literally catch a glimpse of the color separation on the screen manifesting itself as a brief splash of color. This is the so called ‘rainbow effect’; it arises mainly when there is a small moving bright object over a predominantly dark background.

The use of new color wheel design rotating at substantially higher speeds (several 1000 revs per minute), has significantly reduced the occurrence of rainbows. In fact, as things stand today, the majority of people who watch a DLP never see rainbows at all, and the few who do usually see them only occasionally. If this were not the case, then DLP would not lead the rear projection TV world.Mitsubishi LaserVue L75A94 - Click for review

At the same time, if you happen to be one of those people that are sensitive to this rainbow effect, then we say... avoid traditional lamp-based DLPs; the Mitsubishi DLP LaserVue HDTV shown here does away completely with the color wheel by making use of a three-color laser light engine—one for each primary color—that flashes in sequence to produce the color information.

Another issue with DLP rear projection HDTVs is that these sets tend to introduce a bit more low-level video noise than LCD or LCoS based systems. However, this noise issue is often well controlled by the noise reduction features found on many DLP HDTV sets.

DLP-based systems Pros/Cons Summary list:




Relatively inexpensive

The best sets can exhibit very good black level performance and deep saturated colors.

Their bright image makes these sets suitable for use in well lit rooms.

Have excellent overall image uniformity and image quality.

Compact and light

Possible rainbow effects on traditional lamp-based sets.

More presence of low-level video noise than on other rear projection technologies; however, this is well controlled through the use of noise reduction circuitry.

Regular lamp replacements with traditional HID lamp based DLPs make cost of ownership rather high.

This is the only rear projection TV display technology still available on the market. 

LCD Rear Projection HDTVs

This used to be the second most popular rear projection TV technology at a time when rear projection HDTVs were still the only available big screen TVs for home entertainment. Price-wise, it used to sell at the same price of DLP rear projection HDTVs. Its main advantage over DLP is that LCD rear projection technology is not prone to rainbows. LCD RPTVs use three LCD panels, one for each color, instead of the conventional color wheel separator used in DLPs. In the early days of DLP HDTVs, this used to be a big advantage to those sensitive to rainbows, but the use of higher rev color wheels has practically eliminated the rainbow issue almost completely.

Some non-LCD manufactures tend to argue that due to the organic nature of LCDs, the image quality of LCD RPTVs will degrade over time. While in essence this is true, today’s LCD displays are such that the useful lifetime of the organic matter used in the LCD chip by far exceeds the product life span in actual use.

On the downside, LCD rear projection HDTV technology does not support the same black level performance as that of DLPs and LCoS. This is an inherent technical limitation due to the way LCD work to block light from the light source.

As with all lamp-based RPTVs, traditional lamp-based LCD rear projection HDTVs require regular lamp replacement that may eventfully lead to a high cost of ownership. And like their LCoS counterparts, LCD-based rear projection display technology suffers more from white-field uniformity issues than DLP; this non-uniformity becomes more apparent when displaying extensive flat content over the whole screen area.

Another disadvantage of LCDs is mainly one of image quality, more specifically image pixel breakup as a result of what is referred to as screen-door effect. This mainly happens with lower resolution 720p HDTVs when viewing takes place at too close a distance to the screen, in which case the viewer may start noticing the space between adjacent pixels – leading to what may appear as a faint grid of pixels. With 1080p HDTVs, this pixel break-up is practically a non-issue thanks to the higher pixel-fill. However, if you sit at too close a distance, it is still possible to see the pixel structure.

LCD-based systems Pros/Cons Summary list:




Not so expensive with a price tag that is close to that of DLPs.

No rainbow effect

Bright image make these sets suitable for use in a well lit environment.

Compact and light

Blacks are not as deep as the best DLP or LCoS RPTVs; similarly, color saturation is not among the best in RPTV technology.

Visible screen-door effect especially on 720p HDTVs.

LCD sets are more prone to screen uniformity issues.

As with DLPs, traditional lamp-based sets require regular lamp replacements, making cost of ownership high.


LCoS Rear Projection HDTVs

LCoS (Liquid Crystal on Silicon) represents an interesting rear projection HDTV technology that is a hybrid between DLP and LCD. Like DLP, it is a reflective display technology that uses liquid crystals instead of the individual mirrors on a DMD chip to modulate the light falling onto the reflective silicon substrate. And like LCD, it is also a transmissive technology in that light has to pass through the liquid crystals prior to reaching the substrate.

Thus, like their DLP counterparts, LCoS rear projection HDTVs are characterized by excellent black levels and saturated colors. Images do not exhibit any pixel breakup thanks to a greater pixel fill than that possible with LCDs.

Equally important with those sensitive to rainbows, rainbows are not an issue with LCoS in that like LCD, LCoS-based rear projection technology makes use of a three-chip set-up, one for each of the three primary colors.

On the downside, like LCD, LCoS technology suffers from some brightness uniformity. LCoS is also the most expensive of all rear projection technologies.

LCoS technology was originally supported by major TV makers like Philips, Mitsubishi, and Toshiba; these however left the LCoS rear projection business at the early stages of its development in favor of other TV technologies. The only two major TV makers that eventually employed this rear projection technology were Sony with its SXRD (Silicon X-tal Reflective Display) brand and JVC with the HD-ILA (High Definition Direct-drive Image Light Amplifier) brand.

LCoS-based systems Pros/Cons Summary list:




Excellent black levels and deep saturated colors

No rainbow effects

Very good pixel fill with a smooth film-like image; no screen door effect

Bright image makes these sets suitable for use in well lit rooms.

Compact and light

LCoS RPTVs are among the most expensive rear projection HDTVs

Like LCD, LCoS are more prone to screen uniformity issues

As with all traditional lamp based sets, regular lamp replacements make cost of ownership rather high.

Remaining brands are Sony and JVC with Sony announcing that it will leave the market by February 2008.

Making the Choice

If you think rear projection represents a possible solution to your needs, we suggest visiting our updated rear projection TV review page for 2012 HDTVs.

For a better understanding of the advantages and limitations of rear projection HDTVs with respect to other large area display technologies in common use today, please check our Rear Projection TV Facts discussion page.

Buying Options for DLP Rear Projection 3D HDTVs

Search for 3D DLP HDTVs at amazonAmazon offers a most complete range of RPTVs, often at significantly reduced prices. While at amazon...

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