19 Jul 10 Projectors: LCD Verses DLP (The downfall of DLP technology)
The typical question that is asked when acquiring a new projector for the home, office, or classroom is: will I buy an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two most common projector imaging technologies. With so many company brands and types available, it can be overwhelming for the buyer to choose between these technologies. It comes down to the fact that LCD projectors provide far better image quality and colour accuracy. The next paragraph will tell you why DLP projectors struggle with reproducing a similar rate of image quality.
Think of a set of blinds in your house for your bedroom window. With the twist of a rod you can turn the shutters open or closed, according to if you want to let light in or not. And such is exactly how an LCD projector functions. Each pixel functions like its own 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 pros like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from the time the projector is turned on to when the image reaches your screen is vitally important to image quality, brightness and colour accuracy. LCD projectors project white light from the lamp by dividing it into red, blue and green components, by three mirrors which direct the coloured light to 3 separate LCD panels. The 3 LCD panels create the elements of the image by shining each pixel on and off. The pixels are then meshed in a glass prism to form the projector image. A significant point to know about LCD projectors is that all three colours are directed onto your screen at once. The way a DLP projector works is widely different and even the produced 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 approach to forming an image casts 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 sent in sequence on the screen, one colour at a time. The viewer’s vision will then draw each coloured element of the image into the total image. In LCD projectors, all colours are available all the time to form the top level of brightness and spectacular colour accuracy. In DLP, only one colour is available at once, and so causing lower colour brightness and accuracy. Some manufacturers have added a white segment for the colour wheel to improve brightness generally, but this also degrades colour accuracy.
I read in forums all the time that DLP gives a higher contrast ratio and thus must be superior. 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 machine is able to produce. DLP projectors do provide high contrast specifications in comparison to most LCD projectors. At first glance, this can seem to be a benefit, however, in the real world, the true black level is determined by the ambient light in the room while the projector is being utilised. Do not be tricked 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 typical artifact that a DLP projector shows with moving images is colour break up. Colour break up is to be expected in DLP systems because moving images change position between the time red, blue and green colours are shone. LCD projectors do not have this downside because all colours are delivered with the others. DLP developers have formed 3DLP solutions using 3 chips to resolve the colour break up problem, but the price of these projectors make them not practical for the majority of businesses and consumers.
Another variance between LCD and DLP is how they compensate for the refractive qualities of light. Jump back to high school science, and recall when they taught you how the different colours of light refract differing amounts when projected through the same lens. The disadvantage with DLP projectors is that they utilise the one same panel with the same lens to project Red, Blue and Green. All 3 colours are different and refract light in different ways. Usually with a DLP projector, some yellow colour will show above and a superfluous blue will show below an image of something as simple as a single black line. In manufacturing LCD projectors can be adjusted to minimize these effects on the projected image, as each colour is refracted on its own LCD panels.
The isolated actual advantage (excluding price) with taking a DLP projector is its overall smaller size and weight. However, this is only relevant for transporting the device and has to be traded off against the image superiority of LCD projectors. If the result of the picture quality is crucial to you, then the answer is easy. Take an LCD projector! LCD projectors will always show bright, colourful images with fewer image mistakes. If you need to know more about LCD technology in more detail, check out this spectacular resource website: Explore 3LCD. If you have any more questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s number one 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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