Projectors: LCD Verses DLP (The downfall of DLP technology)
The common question customers ask when buying a new projector for the home, office, or classroom is: do I purchase an LCD projector or a DLP projector? LCD, an acronym for ‘liquid crystal device’ and DLP, short for ‘digital light processing’ are the two top projector imaging technologies. With so many different brands and types available, it can be challenging for consumers to decide between both technologies. Ultimately LCD projectors have superior image quality and colour accuracy. The next part of this article explains why DLP projectors struggle with reproducing a comparable standard of image quality.
It’s like a set of blinds in your room over your bedroom window. By pulling a rod you can make the shutters open or closed, depending on whether you want to let light in or not. And this is exactly how an LCD projector operates. Each pixel works like its own shutter on a set of blinds to either send light through or to block it. DLP on the other hand is made up 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 the point when the projector is switched on to when the image reaches your screen is absolutely important in regard 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 send the coloured light to 3 separate LCD panels. The 3 LCD panels make the elements of the image by shining each pixel on and off. The pixels are then combined in a glass prism to send the projector image. A significant point to remember about LCD projectors is that all three colours are projected onto your projector screen all at once. The way a DLP projector works is vastly different and even the way an image shows up is not the same. With DLP, white light from the lamp is processed through a turning colour wheel with transparent red, blue and green segments, at speeds up to 11,000 rpm/s. This way of making an image creates a sequence of red, blue and green light. The millions of micro mirrors mentioned above reflect the coloured light on the pixels to form the image elements. The elements of the image are cast in sequence on the screen, one colour at a time. The viewer’s eye will then combine each coloured element of the image into the single total image. In LCD projectors, all colours are available all the time to form the highest brightness and spectacular colour accuracy. In DLP, just one colour is available at once, and so resulting in lower colour brightness and accuracy. Some designers have placed a white segment in the colour wheel to improve brightness overall, but this further lessens colour accuracy.
I read 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 projector is capable of producing. DLP projectors do have high contrast specifications when compared to most LCD projectors. At one glance, this seems to be a plus, however, in truth, the true black level is determined by the ambient light in the room when the projector is utilised. Do not be duped by contrast specifications on websites and in brochures.
When the content you are trying to view needs moving images, DLP projection technology also has image errors, or ‘artifacts’. The most commonplace artifact that a DLP projector forms with moving images is colour break up. Colour break up is incontrovertible in DLP systems because moving images change position between the time red, blue and green colours are pulled up. LCD projectors do not have this problem because all the colours are delivered with the others. DLP developers have created 3DLP solutions using 3 chips to resolve the colour break up error, but the cost of these projectors make them not practical for the majority of businesses and consumers.
Another difference between LCD and DLP is how they balance for the refractive qualities of light. Think back to high school science, and recall when they taught you how the different colours of light refract different amounts when projected through the same lens. The problem with DLP projectors is that they utilise the one same panel and the same lens to project Red, Blue and Green. All 3 colours are obviously different and refract light differently. Most of the time with a DLP projector, a superfluous yellow colour will show above and an extra blue will show below something as simple as a lone black line. While being built LCD projectors can be adapted to remove these effects on the projected image, as each colour is processed on separate LCD panels.
The only true advantage (excluding price) with deciding on a DLP projector is its smaller overall 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 resulting picture quality is vital to you, then the decision is easy. Go for an LCD projector! LCD projectors will consistently create bright, colourful images with fewer image imperfections. If you want to find out more about LCD technology in more detail, have a look at this fantastic resource website: Explore 3LCD. If you have any additional questions, visit Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s top online shop 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.
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