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: do I get an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, standing for ‘digital light processing’ are the two most popular projector imaging technologies. With so many different brands and different types available, it can be difficult for consumers to make a choice between these technologies. Ultimately LCD projectors offer better image quality and colour accuracy. The article below will tell you why DLP projectors struggle with reproducing a comparable level of image quality.
Imagine a set of blinds in your household over your bedroom window. By a twist of a rod you can make the shutters open or closed, according to whether you want to let light in or not. And that is exactly how an LCD projector behaves. Each pixel works like its own shutter on a set of blinds to either allow 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 point when the projector switches on to when the content reaches your screen is absolutely important with regard to image quality, brightness and colour accuracy. LCD projectors shine white light from the lamp by separating it into red, blue and green components, by three mirrors which project the coloured light to 3 separate LCD panels. The 3 LCD panels cast 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. Something to understad about LCD projectors is that all three colours are projected onto your projector screen all at once. The way a DLP projector functions is very different and even the way an image appears is not the same. With DLP, white light from the lamp is directed through a spinning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of 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 cast 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. Using LCD projectors, all colours are available all the time to deliver the best brightness and superb colour accuracy. In DLP, only one colour is available at any given time, and so resulting in lower colour brightness and accuracy. Some developers have put a white segment in the colour wheel to improve overall brightness, but this also damages colour accuracy.
I find in forums all the time that DLP gives a higher contrast ratio and therefore 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 projector is able to produce. DLP projectors do provide high contrast specifications compared to many LCD projectors. At a glance, this must be an advantage, however, in real life, the true black level is determined by the ambient light in the room when the projector is being used. Do not be fooled by contrast specifications on websites and in brochures.
When the content you want to bring to life has moving images, DLP projection technology can also create image imperfections, or ‘artifacts’. The most typical artifact that a DLP projector displays 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 characteristic because the colours are projected with the others. DLP developers have come up with 3DLP solutions using 3 chips to fix the colour break up error, but the price tag of these projectors make them impractical for many businesses and consumers.
Another variance between LCD and DLP is how they make up for the refractive qualities of light. Take yourself back to high school science, and recall how different colours of light refract varied 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 different and refract light differently. Often with a DLP projector, a superfluous yellow colour will come up above and some extra blue will show below something as simple as a straight black line. In manufacturing LCD projectors can be adjusted to remove these effects on the projected image, because each colour is refracted on separate LCD panels.
The sole veritable buy point (excluding price) with choosing a DLP projector is its smaller size and weight. However, this is only relevant with regard to 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 decision is no-brainer. Take an LCD projector! LCD projectors will constantly create bright, colourful images with fewer image imperfections. If you wish to know more about LCD technology in more detail, see this tremendous resource website: Explore 3LCD. If you have any more questions, jump onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager for Projector Central, Australia’s premier online provider for projectors. Brisbane-based, Projector Central has served Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
