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

July 19th, 2010

The common question that is asked when looking for a new projector for the home, office, or classroom is: would I take an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many business brands and models available, it can be overwhelming for consumers to pick between those technologies. The simple fact of the matter is that LCD projectors provide superior image quality and colour accuracy. The next paragraph will tell you why DLP projectors struggle with projecting the same standard of image quality.

Think of a set of blinds in your house over your bedroom window. By a twist of a rod you can have the shutters open or closed, depending on if you want to let light in or not. And this is exactly how an LCD projector behaves. Each pixel works like a unique shutter on a set of blinds to either shine light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as the experts like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the point at which the projector is turned on to when the picture reaches your screen is absolutely important to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by splitting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 separate LCD panels. The 3 LCD panels make the elements of the image by processing each pixel on and off. The pixels are then projected in a glass prism to send the projector image. A point to realise about LCD projectors is that all three colours are sent onto your projector screen simultaneously. The way a DLP projector works is vastly different and even the produced image shows up 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 approach to making an image forms a sequence of red, blue and green light. The millions of micro mirrors as described above reflect the coloured light on the pixels to create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewer’s eye will then draw each coloured element of the image into the complete image. Using LCD projectors, all colours are available all the time to deliver top brightness and great colour accuracy. In DLP, only one colour is available at a time, and so causing lower colour brightness and accuracy. Some DLP developers have included a white segment in the colour wheel to improve brightness overall, but this goes and detracts from colour accuracy.

I read in forums all the time that DLP has a higher contrast ratio and ergo must be better. For those who are unaware, 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 able to produce. DLP projectors do have high contrast specifications when compared to the majority of LCD projectors. At first glance, this must be an advantage, however, in reality, the true black level is determined by the ambient light in the room when the projector is utilised. Do not be fooled by contrast specifications on websites and in brochures.

When the content you are trying to see needs moving images, DLP projection technology also creates image marks, or ‘artifacts’. The most typical artifact that a DLP projector forms with moving images is colour break up. Colour break up is unavoidable in DLP systems because moving images change position between the time red, blue and green colours are displayed. LCD projectors do not have this problem because every colour is processed with the others. DLP manufacturers have come up with 3DLP solutions using 3 chips to solve the colour break up issue, but the price tag of these projectors make them almost impossible for the large part of businesses and consumers.

Another variance between LCD and DLP is how they balance for the refractive qualities of light. Jump back to high school science, and remember how different colours of light refract differing amounts when projected through the same lens. The downfall with DLP projectors is that they utilise 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 different ways. Usually with a DLP projector, a spill of yellow colour will come up above and a spill of blue will come up below an image containing something as simple as a straight black line. In manufacturing LCD projectors can be fixed to reduce these effects on the projected image, because each colour is processed on isolated LCD panels.

The one actual plus (excluding price) with going with a DLP projector is its smaller overall size and weight. However, this is only relevant with regard to mobility and needs to be traded off against the image advantages of LCD projectors. If resulting picture quality is vital to you, then the solution is no-brainer. Choose an LCD projector! LCD projectors will consistently make bright, colourful images with fewer image blips. If you want to find out more about LCD technology in more detail, see this fabulous resource website: Explore 3LCD. If you have any other questions, jump onto Projector Central and send me an email.

Jonathan King is the sales and marketing manager at Projector Central, Australia’s premier online shop for projectors. Based in Brisbane, Projector Central has been servicing Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.

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