DLP Projectors

LCD and DLP projector technology

There are two main types of multimedia projector technology on the market available to consumers which most people considering a new projector will have heard of: LCD technology and DLP technology. When buying a new projector this is frequently one of the first decisions you will make: should I buy a DLP projector? Or should I get an LCD one?

Some people will prefer one kind of projector technology for various reasons, while others will prefer the other kind. Often people are not sure which technology is which or what the differences between the two types of technology are. In actual fact, there are some very big differences between LCD and DLP projector technology despite the fact that they both do essentially the same job: projecting an image on to a screen. Both DLP and LCD have their own advantages and corresponding disadvantages which will affect which type of projector technology is better for you and your presentation application.

This Bamboo AV Advice article will focus on digital light processing (DLP) projector technology. Where DLP projector technology came from, how DLP projectors work to produce an image, and the advantages and disadvantages of DLP technology will be covered in detail in the following article.

What is DLP technology?

Digital Light Processing (DLP) is a proprietary technology developed and owned by the company Texas Instruments (TI) for use in multi media projectors. Originally developed by Larry Hornbeck in 1987, Digital Light Processing is now currently one of the most regularly implemented projector technologies, and is the main rival to LCD projector technology.

How DLP technology produces an image.

Central to how a DLP projector displays an image is the Digital Micromirror Device (DMD) chip housed inside the projector. The DLP chip contains thousands of mirrors, each of which is used to represent a single pixel. To form the picture, the image source sends information to the projector, which causes the mirrors to be adjusted on both a vertical and horizontal axis, therefore varying the amount of light that can be projected through the lens.

The way in which DLP projectors generate colours is dependant on the number of Digital Micromirror Device chips inside the projector. The way in which a single chip DLP projector and a three chip DLP projector produces an image is very different. The two types of DLP projectors will be discussed in more detail below.

Single chip DLP projectors

Single chip DLP projectors use an image production system which includes a revolving colour wheel, first developed in the 1950s for use with original colour televisions. The colour wheel is the central component used for generating colours in single chip projectors. It is usually divided into three segments, one for each primary colour (red, blue, and green), although some DLP projector manufacturers include a forth clear white zone in the colour wheel to help enhance the brightness of the projected image at the expense of a reduced colour saturation.

The colour wheel is placed between the DMD chip and the projector lamp, and is spun in sync with the DMD chip. Consequently the red part of the colour wheel is in line with the red section of the DMD chip when in front of the lamp. This cycle continues for each colour, meaning that each colour is projected one after another. If the projector has a slow spin speed then occasionally the individual beams can become visible to the viewer.

The image below displays the internal working mechanism of a single chip DLP projector.

Internal mechanism of a single chip DLP projector

Three chip DLP projectors

Three chip DLP projectors are the highest quality projectors currently available in terms of the image they can output. However, as the price of the cheapest three-chip DLP projector starts at over $10,000, their market penetration is limited to extremely expensive, big budget home theatres and commercial environments which necessitate an extremely high quality image being projected.

Since a three-chip DLP projector houses three Digital Micromirror Device chips, each one can be dedicated to processing each primary colour – red, green and blue. A prism is used to split the light from the lamp into the three primary colours, which is then forwarded to the corresponding DMD chip. Since each colour has a dedicated chip it has a longer time to be rendered, resulting in a higher quality image that does not suffer from flickering or the rainbow effect which can be problem in single chip DLP projectors. To project the image, the colours from each of the three DLP chips are recombined and sent out via the projector lens.

The image below displays the internal working mechanism of a three chip DLP projector.

Internal mechanism of a three chip DLP projector

What are the advantages of DLP projectors?

Less “chicken wire” effect

Since DLP projector panels have a much tighter pixel structure (the tiny mirrors are placed very close to each other), there is far less of a “chicken wire” effect in which the panel patterns become visible on screen, causing an image to appear pixelated.

Higher contrast images

The technology used in DLP projectors allows for a better quality, far higher contrast image to be projected. LCD contrast ratios max out at 1000 to 1 where as DLP projectors can range up to 4000 to 1.

Increased portability

Since DLP projectors are composed of fewer components they can be housed in smaller units. This makes them more portability than their LCD counterparts.

Increased operating life

The reduced number of parts in a DLP projector means that DLP projectors require less maintenance. The fact that they have less parts to go wrong means that inevitably they have a greater lifespan than LCD projectors.

No “dead pixels”

Dead pixels (where a pixel becomes permanently stuck in an “on” or “off” position) are extremely rare in DLP projectors. In LCD projectors they are much more common and can become an annoyance if clusters of dead pixels occur in the same place.

What are the disadvantages of DLP projectors?

Rainbow effect

The “rainbow effect” is experienced by some users of DLP projectors. This can happen when the viewer’s eye moves from one side of the screen to another, or the images on screen make fast movements. When a user experiences the “rainbow effect”, objects on the screen can appear to have a trailing shadow of rainbow colours. However, it is important to note that the frequency and intensity of the rainbow effect is dependant on the specific viewer. It may cause headaches in some, where as it may be practically unnoticeable to others.

Light leakage

In DLP projectors, especially lower-end models, light can reflect off stray edges of the tiny mirrors on some DLP chips, causing a grey bar to frame the edge of the image projected. This light leakage problem can be especially noticeable and irritating when used in the home theatre context as it can ruin the immersion of films for some viewers.

Increased price

When choosing a projector you should expect to pay a higher price for a DLP projector that has otherwise identical technical specifications to an LCD projector.

DLP projector applications

The most notable application of three chip DLP projector technology – as far as publicity is concerned – is its use in IMAX theatres. This has lent further support to the belief that three-chip DLP projectors are the best choice for home theatre owners desiring the best possible image. DLP projectors often have far higher contrast ratios to LCD projectors, and can also render much deeper blacks. The problem is that this high image quality comes at a high price.

Single-chip type DLP projectors are recommended for those projector users who are consistently giving presentations on the road. The reduced number of components (as compared to an LCD projector) make DLP projectors a better choice for easier portability, while the strong image quality makes a good impression on the audience and ensures the presentation can be clearly seen.

DLP projector manufacturers

DLP projectors are generally less common in the audio visual marketplace than LCD projectors. This is mainly because DLP manufacturers have to pay to use Digital Light Processing technology since it is a proprietary technology owned by Texas Instruments.

Furthermore, as the technology used in Digital Light Processing projectors renders better quality images, it also costs manufacturers more to produce, making it less attractive for production for many companies.

The upshot of this cost of manufacturing is that cheap copy DLP projectors are practically nonexistent, so you can be assured that whichever brand you buy, you are buying a good quality projector. DLP products have won awards year after year at the Consumer Electronics Show for their great quality image production.

There are a number of manufacturers that specialise in producing DLP projectors but the most well known manufactures are Sharp, Panasonic, Mitsubishi and Toshiba.

We hope that this Bamboo AV Advice article has been useful to you!

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