Projectors: LCD Verses DLP (The downfall of DLP technology)

The typical question customers ask when looking for a new projector for the home, office, or classroom is: would I purchase an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, an acronym for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many different brands and models available, it can be confusing for customers to make a choice between these technologies. The simple fact of the matter is that LCD projectors give better image quality and colour accuracy. The article below explains why DLP projectors struggle with bringing up an equal standard of image quality.

Imagine a set of blinds in your house over your bedroom window. By a twist of a rod you can make the shutters open or closed, depending on if you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel operates like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element functions to either reflect light or block it.

How the light source is processed from the time the projector is turned on to when the content reaches your screen is vitally significant to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by separating it into red, blue and green components, by three mirrors which project the coloured light to 3 separate LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then simultaneously processed in a glass prism to form the projector image. A point to understad about LCD projectors is that all three colours are sent onto your projected surface all at the same time. The way a DLP projector works is widely different and even the way an image shows up is not the same. With DLP, white light from the lamp is sent through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to making an image requires a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to form the image elements. The elements of the image are displayed in sequence on the screen, one colour at a time. The viewer’s vision will then pull together each coloured element of the image into a single complete image. In LCD projectors, all colours are available all the time to offer the best brightness and fantastic colour accuracy. In DLP, only one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some DLP designers have put a white segment into the colour wheel to improve brightness overall, but this further lessens colour accuracy.

I see in forums all the time that DLP gives a higher contrast ratio and as such must be superior. For those who don’t know, the contrast ratio is a measure of a display system defined as the ratio of the luminance of the brightest white to that of the darkest black that the system is able to produce. DLP projectors do provide high contrast specifications as compared to most LCD projectors. At one glance, this must be an advantage, however, in truth, the true black level is determined by the ambient light in the room in which the projector is being utilised. Do not be hoodwinked by contrast specifications on websites and in brochures.

When the content you are trying to see includes moving images, DLP projection technology also creates image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector shows with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change up between the time red, blue and green colours are pulled up. LCD projectors do not have this disadvantage because all the colours are processed with the others. DLP builders have formed 3DLP solutions using 3 chips to resolve the colour break up problem, but the expense of these projectors make them hardly practical for the majority of businesses and consumers.

Another differentiation between LCD and DLP is how they make up for the refractive qualities of light. Think back to high school science, and recall when they taught you how various colours of light refract different amounts when directed through the same lens. The disadvantage with DLP projectors is that they use the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light in a different way. Usually with a DLP projector, some yellow colour will be projected above and a spill of blue will be projected below an image as simple as a lone black line. In building LCD projectors can be adjusted to take away these effects on the projected image, because each colour is projected on a separate LCD panels.

The sole true benefit (excluding price) with taking a DLP projector is its smaller overall size and weight. However, this is only relevant in regard to portability and must be traded off against the image advantages of LCD projectors. If resulting picture quality is vital to you, then the answer is easy. Go for an LCD projector! LCD projectors will constantly make bright, colourful images with fewer image mistakes. If you need to ask more about LCD technology in more detail, have a look at this tremendous resource website: Explore 3LCD. If you have any additional questions, go to Projector Central and send me an email.

Jonathan King is the sales and marketing manager at Projector Central, Australia’s top online store for projectors. Brisbane-based, Projector Central has been servicing Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.