Projectors: LCD Verses DLP (The downfall of DLP technology)
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The common question customers ask when acquiring a new projector for the home, office, or classroom is: do I buy an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two top projector imaging technologies. With so many brands and models available, it can be challenging for clients to choose between the two technologies. The fact is that LCD projectors provide superior image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with creating a similar grade of image quality.
Imagine a set of blinds in your home covering your bedroom window. By pulling a rod you can have the shutters open or closed, according to whether you want to let light in or not. That is exactly how an LCD projector works. Each pixel functions like a single shutter on a set of blinds to either allow 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 point when the projector turns on to when the image reaches your screen is absolutely significant to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by cutting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 different LCD panels. The 3 LCD panels create the elements of the image by turning each pixel on and off. The pixels are then combined in a glass prism to create the projector image. A significant point to remember about LCD projectors is that all three colours are projected onto your screen all at the same time. The way a DLP projector operates is widely different and even the produced image looks is not the same. With DLP, white light from the lamp is processed through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of projecting 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 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 pull together each coloured element of the image into the total image. With LCD projectors, all colours are available all the time to deliver high brightness and great colour accuracy. In DLP, just one colour is available at a time, resulting in lower colour brightness and accuracy. Some manufacturers have put a white segment for the colour wheel to improve overall brightness, but this also lessens colour accuracy.
I read in forums all the time that DLP offers a higher contrast ratio and ergo must be superior quality. For those uncertain, 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 possess high contrast specifications as compared to a majority of LCD projectors. At one glance, this seems to be a benefit, however, in reality, the true black level is determined by the ambient light in the room in which the projector is used. Do not be duped by contrast specifications on websites and in brochures.
When the content you wish to bring to life needs moving images, DLP projection technology also has image imperfections, or ‘artifacts’. The most common 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 pulled up. LCD projectors do not have this problem because every colour is projected simultaneously. DLP developers have created 3DLP solutions using 3 chips to resolve the colour break up error, but the price of these projectors make them not practical for the large part of businesses and consumers.
Another difference between LCD and DLP is how they match the balance for the refractive qualities of light. Take yourself back to high school science, and remember when they taught you how different colours of light refract varied amounts when passing through the same lens. The disadvantage with DLP projectors is that they have the one same panel for the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in a different way. Usually with a DLP projector, some extra yellow colour will appear above and a superfluous blue will be projected below something as simple as a straight black line. In manufacturing LCD projectors can be adjusted to take away these effects on the projected image, because each colour is refracted on a separate LCD panels.
The isolated real buy point (excluding price) with deciding on a DLP projector is its smaller size and weight. However, this is only relevant in regard to mobility and needs to be traded off against the image superiority of LCD projectors. If overall picture quality is vital to you, then the answer is easy. Take an LCD projector! LCD projectors will constantly produce bright, colourful images with fewer image imperfections. If you want to learn more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any additional questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with 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.
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