Projectors: LCD Verses DLP (The downfall of DLP technology)
The most common question customers ask when purchasing a new projector for the home, office, or classroom is: would 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 business brands and different models available, it can be difficult for the buyer to make a decision between the two technologies. It comes down to the fact that LCD projectors give better image quality and colour accuracy. The following article will explain why DLP projectors struggle with projecting an equal level of image quality.
Think of a set of blinds in your household over your bedroom window. By pulling a rod you can make the shutters open or closed, according to if 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 pass light through or to block it. DLP on the other hand is constructed of millions of microscopic mirrors or ‘pixel elements’ as experts like to call them. Each pixel element operates 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 image reaches your screen is absolutely important to image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by separating it into red, blue and green components, by three mirrors which transfer the coloured light to 3 separate LCD panels. The 3 LCD panels cast the elements of the image by switching each pixel on and off. The pixels are then combined in a glass prism to deliver the projector image. A significant point to remember about LCD projectors is that all three colours are sent onto your wall at once. The way a DLP projector runs is widely different and even how an image appears is not the same. With DLP, white light from the lamp is sent through a rotating colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This method of projecting an image requires 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 displayed in sequence on the screen, one colour at a time. The viewer’s vision will then draw each coloured element of the image into a complete image. From LCD projectors, all colours are available all the time to deliver the best brightness and spectacular colour accuracy. In DLP, just one colour is available at a time, and so resulting in lower colour brightness and accuracy. Some developers have added a white segment in the colour wheel to improve overall brightness, but this then damages colour accuracy.
I hear in forums all the time that DLP gives a higher contrast ratio and therefore must be superior. For those 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 system is capable of. DLP projectors do provide high contrast specifications as compared to most LCD projectors. At one glance, this appears to be an advantage, however, in truth, the true black level is determined by the ambient light in the room in which the projector is used. Do not be tricked by contrast specifications on websites and in brochures.
When the content you want to view requires moving images, DLP projection technology can also create image marks, or ‘artifacts’. The most commonplace artifact that a DLP projector creates with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images keep changing between the time red, blue and green colours are displayed. LCD projectors do not have this downside because all the colours are delivered at once. DLP developers have created 3DLP solutions using 3 chips to fix the colour break up error, but the expense of these projectors make them hardly practical for most businesses and consumers.
Another difference between LCD and DLP is how they make up for the refractive qualities of light. Take yourself back to high school science, and recall when they taught you how different 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 and the same lens to project Red, Blue and Green. All 3 colours are obviously not the same and refract light at different levels. Most of the time with a DLP projector, some yellow colour will show above and some blue will show below something as simple as a straight black line. In building LCD projectors can be set to reduce these effects on the projected image, as each colour is directed on isolated LCD panels.
The sole veritable benefit (excluding price) with buying a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to portability and needs to be traded off against the image advantages of LCD projectors. If resulting picture quality is crucial to you, then the choice is no-brainer. Go for an LCD projector! LCD projectors will always produce bright, colourful images with fewer image imperfections. If you need to ask more about LCD technology in more detail, have a look at this tremendous 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 of Projector Central, Australia’s number one online store for projectors. Based in Brisbane, Projector Central has serviced Australia for 15 years. For data projectors in Brisbane and Interactive Whiteboards, contact Projector Central today.
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