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

July 19th, 2010

The most typical question that is asked when buying a new projector for the home, office, or classroom is: do I get an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many company brands and models available, it can be challenging for customers to pick between the two technologies. It comes down to the fact that LCD projectors have far superior image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with creating a similar level of image quality.

Imagine a set of blinds in your house over your bedroom window. By twisting a rod you can turn the shutters open or closed, according to whether you want to let light in or not. This is exactly how an LCD projector behaves. Each pixel operates like its own shutter on a set of blinds to either send light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as the professionals like to call them. Each pixel element functions to either reflect light or block it.

How the light source is processed from when the projector is switched on to when the content reaches your screen is absolutely significant in regard to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by dividing it into red, blue and green components, by three mirrors which direct the coloured light to 3 stand alone LCD panels. The 3 LCD panels make the elements of the image by processing each pixel on and off. The pixels are then combined in a glass prism to form the projector image. Something to realise about LCD projectors is that all three colours are sent onto your screen all at the same time. The way a DLP projector operates is very different and even how an image looks is not the same. With DLP, white light from the lamp is projected through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of making an image creates a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to produce the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eye will then put together each coloured element of the image into the single total image. In LCD projectors, all colours are available all the time to deliver top brightness and fantastic colour accuracy. In DLP, only one colour is available at a time, causing lower colour brightness and accuracy. Some DLP manufacturers have added a white segment for the colour wheel to improve general brightness, but this also degrades colour accuracy.

I read in forums all the time that DLP provides a higher contrast ratio and thus must be better. For those who are unsure, 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 technology is capable of. DLP projectors do have high contrast specifications when compared to a majority of LCD projectors. At first glance, this appears to be a benefit, however, in reality, the true black level is determined by the ambient light in the room while the projector is used. Do not be hoodwinked by contrast specifications on websites and in brochures.

When the content you are trying to project needs moving images, DLP projection technology also has image errors, or ‘artifacts’. The most typical artifact that a DLP projector displays with moving images is colour break up. Colour break up is inherent in DLP systems because moving images keep changing between the time red, blue and green colours are shone. LCD projectors do not have this disadvantage because all the colours are sent at the same time. DLP designers have created 3DLP solutions using 3 chips to solve the colour break up artifacts, but the price tag of these projectors make them impractical for the large part of businesses and consumers.

Another point of difference between LCD and DLP is how they balance for the refractive qualities of light. Take yourself back to high school science, and they taught you how various colours of light refract varied amounts when passing 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 different and refract light in a different way. Often with a DLP projector, a superfluous yellow colour will appear above and a spill of blue will show below an image as simple as a lone black line. In building LCD projectors can be set to remove these effects on the projected image, as each colour is refracted on its own LCD panels.

The isolated real advantage (excluding price) with going with a DLP projector is its smaller overall size and weight. However, this is only relevant to transport and needs to be traded off against the image plusses of LCD projectors. If overall picture quality is important to you, then the answer is simple. Choose an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image imperfections. If you wish to ask more about LCD technology in more detail, have a gander at this spectacular resource website: Explore 3LCD. If you have any persisting questions, get onto Projector Central and send me an email.

Jonathan King is the sales and marketing manager of Projector Central, Australia’s leading online store for projectors. Based in Brisbane, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.

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