Projectors: LCD Verses DLP (The downfall of DLP technology)
The most typical question asked when looking for a new projector for the home, office, or classroom is: will I buy an LCD projector or a DLP projector? LCD, short for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many brands and different types available, it can be difficult for customers to decide between the two technologies. Ultimately LCD projectors provide far better image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with bringing up an equal level of image quality.
Imagine a set of blinds in your household on your bedroom window. By twisting a rod you can turn the shutters open or closed, according to if you want to let light in or not. Such is exactly how an LCD projector functions. Each pixel works like a single 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 professionals like to call them. Each pixel element works 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 vitally significant for image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by cutting it into red, blue and green components, by three mirrors which project 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 projected in a glass prism to create the projector image. Something to know about LCD projectors is that all three colours are projected onto your projected surface all at the same time. The way a DLP projector runs is widely different and even the way an image comes out is not the same. With DLP, white light from the lamp is directed 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 as described above reflect the coloured light on the pixels to form 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 whole image. In LCD projectors, all colours are available all the time to create high brightness and superb colour accuracy. In DLP, just one colour is available at once, and so resulting in lower colour brightness and accuracy. Some DLP developers have added a white segment for the colour wheel to improve brightness generally, but this further lessens colour accuracy.
I see in forums all the time that DLP provides a higher contrast ratio and therefore 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 projector is able to produce. DLP projectors do provide high contrast specifications when compared to a majority of LCD projectors. At first glance, this must be a plus, however, in truth, 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 plan to see has moving images, DLP projection technology also has image imperfections, or ‘artifacts’. The most commonplace artifact that a DLP projector displays with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change up between the time red, blue and green colours are displayed. LCD projectors do not have this problem because all colours are delivered with the others. DLP builders have developed 3DLP solutions using 3 chips to fix the colour break up issue, but the price of these projectors make them almost impossible for many 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 recall how the different colours of light refract varied amounts when shone through the same lens. The downfall with DLP projectors is that they take the one same panel with the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light at different levels. Generally with a DLP projector, some yellow colour will be projected above and some extra blue will come up below something as simple as a single black line. During manufacturing LCD projectors can be fixed to minimize these effects on the projected image, because each colour is processed on isolated LCD panels.
The only true advantage (excluding price) with taking a DLP projector is its overall smaller size and weight. However, this is only relevant for portability and must be traded off against the image benefits of LCD projectors. If the result of the picture quality is vital to you, then the answer is a no-brainer. Choose an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image errors. If you wish to learn more about LCD technology in more detail, see this fantastic resource website: Explore 3LCD. If you have any other questions, go to Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s premier online provider for projectors. Based in Brisbane, Projector Central has served Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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