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 take an LCD projector or a DLP projector? LCD, standing for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two top projector imaging technologies. With so many business brands and models available, it can be difficult for clients to pick between these technologies. The fact is that LCD projectors give superior image quality and colour accuracy. The next part of this article will explain why DLP projectors struggle with projecting an equal rate of image quality.
It’s like a set of blinds in your room for your bedroom window. By a twist of a rod you can turn the shutters open or closed, depending on whether you want to let light in or not. Such is exactly how an LCD projector works. Each pixel operates like its own 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 the experts like to call them. Each pixel element works to either reflect light or block it.
How the light source is processed from when the projector is switched on to when the image reaches your screen is absolutely significant with regard to image quality, brightness and colour accuracy. LCD projectors process white light from the lamp by splitting it into red, blue and green components, by three mirrors which project the coloured light to 3 separate LCD panels. The 3 LCD panels form the elements of the image by switching each pixel on and off. The pixels are then projected in a glass prism to form the projector image. Something to realise about LCD projectors is that all three colours are sent onto your screen simultaneously. The way a DLP projector works is widely different and even the way an image appears is not the same. With DLP, white light from the lamp is projected through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This approach to creating 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 produce the image elements. The elements of the image are sent in sequence on the screen, one colour at a time. The viewer’s eyes will then put together each coloured element of the image into a full image. With LCD projectors, all colours are available all the time to offer top brightness and fantastic colour accuracy. In DLP, just one colour is available at a time, causing lower colour brightness and accuracy. Some DLP manufacturers have put 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 has a higher contrast ratio and therefore must be better. For those who are 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 compared to the majority of LCD projectors. At one glance, this can seem to be a plus, however, in truth, the true black level is determined by the ambient light in the room when the projector is being utilised. Do not be tricked by contrast specifications on websites and in brochures.
When the content you plan to project requires moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most common artifact that a DLP projector shows with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change between the time red, blue and green colours are shone. LCD projectors do not have this disadvantage because all the colours are sent with the others. DLP builders have developed 3DLP solutions using 3 chips to fix the colour break up error, but the cost of these projectors make them not practical for the large part of businesses and consumers.
Another point of difference between LCD and DLP is how they balance for the refractive qualities of light. Think back to high school science, and remember how various colours of light refract various amounts when shone through the same lens. The downside 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 different and refract light in different ways. Usually with a DLP projector, some yellow colour will be projected above and a spill of blue will come through below an image of something as simple as a lone black line. In building LCD projectors can be adjusted to reduce these effects on the projected image, because each colour is refracted on a separate LCD panels.
The one real buy point (excluding price) with picking a DLP projector is its overall smaller size and weight. However, this is only relevant with regard to transporting the device and needs to be traded off against the image advantages of LCD projectors. If overall picture quality is important to you, then the answer is easy. Take an LCD projector! LCD projectors will constantly show bright, colourful images with fewer image errors. If you need to know more about LCD technology in more detail, have a gander at this fantastic resource website: Explore 3LCD. If you have any persisting questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager with Projector Central, Australia’s number one online retailer for projectors. Brisbane based, Projector Central has serviced Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
