Projectors: LCD Verses DLP (The downfall of DLP technology)
Posted on July 19, 2010, under Uncategorized.
The typical question heard when looking for a new projector for the home, office, or classroom is: will I purchase 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 popular projector imaging technologies. With so many brands and models available, it can be overwhelming for clients to make a decision between these technologies. Ultimately LCD projectors offer far better image quality and colour accuracy. The following article explains why DLP projectors struggle with creating a similar rate of image quality.
Visualise a set of blinds in your home on your bedroom window. By twisting a rod you can make the shutters open or closed, depending on if you want to let light in or not. And such is exactly how an LCD projector behaves. Each pixel operates like a single shutter on a set of blinds to either pass light through or to block it. DLP on the other hand is formed of millions of microscopic mirrors or ‘pixel elements’ as professionals like to call them. Each pixel element operates to either reflect light or block it.
How the light source is processed from when the projector is switched on to when the picture reaches your screen is ultimately important for image quality, brightness and colour accuracy. LCD projectors direct white light from the lamp by cutting it into red, blue and green components, by three mirrors which transfer the coloured light to 3 different LCD panels. The 3 LCD panels make 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. An important point to understad about LCD projectors is that all three colours are projected onto your wall all at the same time. The way a DLP projector operates is totally different and even the final product of how 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 method of projecting an image forms 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 cast in sequence on the screen, one colour at a time. The viewer’s vision will then put together each coloured element of the image into the single complete image. With LCD projectors, all colours are available all the time to deliver the highest brightness and fantastic colour accuracy. In DLP, only one colour is available at a time, causing lower colour brightness and accuracy. Some designers have added a white segment into the colour wheel to improve overall brightness, but this goes and damages colour accuracy.
I find in forums all the time that DLP provides a higher contrast ratio and as such must be superior. For those who are 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 technology is capable of producing. DLP projectors do have high contrast specifications in comparison to a majority of LCD projectors. At a glance, this must be a benefit, however, in reality, the true black level is determined by the ambient light in the room where the projector is utilised. Do not be fooled by contrast specifications on websites and in brochures.
When the content you plan to project has moving images, DLP projection technology can also create image errors, or ‘artifacts’. The most commonplace 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 position between the time red, blue and green colours are pulled up. LCD projectors do not have this problem because all colours are processed at once. DLP designers have come up with 3DLP solutions using 3 chips to solve the colour break up problem, but the cost of these projectors make them almost impossible for the large part of businesses and consumers.
Another variance between LCD and DLP is how they make up for the refractive qualities of light. Jump back to high school science, and remember how the various colours of light refract various amounts when shone through the same lens. The disadvantage with DLP projectors is that they have the one same panel and the same lens to project Red, Blue and Green. All 3 colours are not the same and refract light in different ways. Often with a DLP projector, a spill of yellow colour will come up above and an extra blue will come through below something as simple as a lone black line. In building LCD projectors can be set to minimize these effects on the projected image, as each colour is projected on isolated LCD panels.
The sole true buy point (excluding price) with going with a DLP projector is its smaller size and weight. However, this is only relevant to transport and must be traded off against the image advantages of LCD projectors. If the outcome of the picture quality is crucial to you, then the choice is simple. Go for an LCD projector! LCD projectors will constantly create bright, colourful images with fewer image errors. If you wish to find out more about LCD technology in more detail, have a gander at this tremendous resource website: Explore 3LCD. If you have any other questions, get onto Projector Central and send me an email.
Jonathan King is the sales and marketing manager at Projector Central, Australia’s number one online retailer for projectors. Based in Brisbane, Projector Central has been serving Australia for 15 years. For data projectors in the Gold Coast and Interactive Whiteboards, contact Projector Central today.
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