Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question that is asked when looking for a new projector for the home, office, or classroom is: should I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two commonplace projector imaging technologies. With so many business brands and types available, it can be confusing for customers to choose between the two technologies. The fact is that LCD projectors give far superior image quality and colour accuracy. The next part of this article tells you why DLP projectors struggle with creating a similar rate of image quality.
It’s like a set of blinds in your house over your bedroom window. By pulling a rod you can turn the shutters open or closed, depending on whether you want to let light in or not. This is exactly how an LCD projector operates. Each pixel works like a unique shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is created of millions of microscopic mirrors or ‘pixel elements’ as pros like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the point when the projector turns on to when the content reaches your screen is ultimately important to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by splitting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 stand alone LCD panels. The 3 LCD panels form the elements of the image by turning each pixel on and off. The pixels are then simultaneously processed in a glass prism to deliver the projector image. A point to realise about LCD projectors is that all three colours are delivered onto your projector screen at the same time. The way a DLP projector functions is widely different and even the produced image looks is not the same. With DLP, white light from the lamp is directed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of projecting 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 form the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eyes will then pull together each coloured element of the image into a single whole image. With LCD projectors, all colours are available all the time to deliver the top level of brightness and great colour accuracy. In DLP, just one colour is available at any given time, and so causing lower colour brightness and accuracy. Some developers have added a white segment into the colour wheel to improve overall brightness, but this further damages colour accuracy.
I see in forums all the time that DLP gives a higher contrast ratio and thus 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 technology is able to produce. DLP projectors do have high contrast specifications when compared to most LCD projectors. At a glance, this appears 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 in use. Do not be hoodwinked by contrast specifications on websites and in brochures.
When the content you want to view needs moving images, DLP projection technology also has image errors, or ‘artifacts’. The most typical artifact that a DLP projector forms with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images keep changing between the time red, blue and green colours are displayed. LCD projectors do not have this characteristic because all colours are sent simultaneously. DLP designers have come up with 3DLP solutions using 3 chips to resolve 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 balance for the refractive qualities of light. Remember back to high school science, and remember when they taught you how the various colours of light refract differing amounts when shone through the same lens. The disadvantage with DLP projectors is that they take 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, a superfluous yellow colour will come up above and an extra blue will appear below an image as simple as a straight black line. While being built LCD projectors can be adapted to take away these effects on the projected image, because each colour is refracted on its own LCD panels.
The one true benefit (excluding price) with buying a DLP projector is its smaller total size and weight. However, this is only relevant in regard to portability and needs to be traded off against the image benefits of LCD projectors. If the result of the picture quality is crucial to you, then the solution is simple. Choose an LCD projector! LCD projectors will always produce bright, colourful images with fewer image imperfections. If you desire to know more about LCD technology in more detail, see this fabulous 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 for Projector Central, Australia’s leading online provider for projectors. Brisbane-based, 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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