Projectors – LCD Vs DLP (The downfall of DLP technology)

The most common question asked when purchasing a new projector, for the home, office or classroom is; do I buy an LCD projector or a DLP projector? LCD, which stands for ‘liquid crystal device’ and DLP, which stands for ‘digital light processing’ are the two most common projector imaging technologies. With so many brands and models available it can be overwhelming for customers to make a choice between both technologies. The fact is LCD projectors offer superior image quality and colour accuracy. The following article explains why DLP projectors struggle with reproducing the same level of image quality.

Imagine a set of blinds in your home covering your bedroom window. With the twist of a rod you can have the shutters open or closed, depending on if you want to let light in or not. This is exactly how an LCD projector works. Each Pixel works like an individual shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is made up of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element works to either reflect light or block it.

How the light source is processed from the time the projector turns on to when the picture reaches your screen is vitally important 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 direct the coloured light to 3 different LCD panels. The 3 LCD panels create the elements of the image by turning each pixel on and off, which are then combined in a glass prism to deliver the projector image. An important point to remember about LCD projectors is that all three colours are projected into your wall at the same time. The way a DLP projector works is vastly different and even the way an image looks 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 approach to creating an image creates a sequence of red, blue and green light. The millions of micro mirrors described above reflect the coloured light on the pixels to create the image elements. The elements of the image are projected in sequence on the screen, one colour at a time. The viewers eyes will then combine each coloured element of the image into a single complete image. With LCD projectors all colours are available all the time to deliver high brightness and fantastic colour accuracy. In DLP, only one colour is available at a time resulting in lower colour brightness and accuracy. Some manufactures have included a white segment into the colour wheel to improve over all brightness, but this further degrades colour accuracy.

I read in forums all the time that DLP has a higher contrast ratio and therefore must be better. 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 producing. DLP projectors do have high contrast specifications compared to most LCD projectors. At first glance, this seems to be an advantage, however, in the real world the true black level is determined by the ambient light in the room when the projector is used. Do not be fooled by contrast specifications on websites and brochures.

When the content you want to view includes moving images, DLP projection technology can also create image errors, or ‘artifacts’. The most common artifact that a DLP projector displays with moving images is colour break up. Colour break up is inherent in DLP systems because moving images change position between the time red, blue and green colours are displayed. LCD projectors do not have this characteristic because all colours are delivered simultaneously. DLP manufacture’s have developed 3DLP solutions using 3 chips to solve the colour break up problem, but the cost of these projectors make them impractical for most businesses and consumers.

Another difference between LCD and DLP is how they compensate for the refractive qualities of light. Take yourself back to high school science and remember how different colours of light refract different amounts when passing through the same lens. The downfall with DLP projectors is that it uses the same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light different. Most of the time with a DLP projector an extra yellow colour will appear above and an extra blue will appear below something as simple as a straight black line. During manufacturing LCD projectors can be adjusted to minimize these effects on the projected image as each colour is processed on separate LCD panels.

The only real advantage (excluding price) with choosing a DLP projector is its overall smaller size and weight. However, this is only relevant for portability and must be traded off against the image advantages of LCD projectors. If overall picture quality is important to you, then the solution is simple. Choose an LCD projector!. LCD projectors will always produce bright, colourful images with less image errors. If you want to learn more about LCD technology in more detail, check out this fantastic resource website Explore 3LCD. If you have any more questions go to Projector Central and send me an email.

Jonathan King is sales and marketing manager for Projector Central, Australia’s leading online store for projectors. Brisbane based, Projector Central has been servicing Australia for 15 years.

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