Projector Display Systems

LCD, DLP, and CRT Projection

LCD projectors (liquid crystal display)

LCD projection is an older and, therefore, less expensive digital projector technology, and the dominant force in the market. Using three LCD panels or prisms (one green, one blue, one red) and a fixed number of pixels, an LCD projector produces a high resolution image with good color definition. LCD projectors use light efficiently and produce a sharp image, which is great for data presentations, but sharpness can be a drawback when you’re watching video because it can cause pixelation, also known as the “screen door” or “chicken wire” effect. Other things to watch out for include dead pixels that are stuck displaying one color. Contrast has also been an area where LCD projectors don’t perform as well, which is particularly relevant for video projection but makes little difference when you’re displaying data in a lighted or partially lighted room. Both these problems are becoming less of an issue thanks to the technological improvements being put to work in the newer LCD projection systems.

DLP projectors (digital light processing)

Digital Light Processing replaces LCD’s panels with a reflective DMD (digital mirror device) chip - three of them in most expensive models - and uses a rotating wheel to produce color. DMD chips are covered with thousands of tiny mirrors, each representing a pixel, which means that, like LCD projectors, the DLP projector is a fixed pixel display system (they both have a fixed number of pixels that they can display). DLP projectors aren’t the cheapest but they’re light-weight (they make great ultra portable projectors for presenters on the go) and project a sharp, bright, high-contrast image, especially the three-chip models. Some DLP projectors have problems with color saturation and accuracy as well as the “rainbow effect” - a visual artifact caused by color separation. Newer machines with faster rotating color wheels, and / or additional color filters have made this less of a concern.

LCOS projectors (liquid crystal on silicon)

Liquid Crystal on Silicon combines the “transmissive” elements of LCD and the “reflective” nature of DLP projection technology. Like LCD, LCoS offers continuous color with its separate red, green and blue chips. The higher pixel density of LCoS projectors results in a high resolution and smooth image with virtually no perceivable pixelation. The machines are large and heavy, so not very portable, and tend to be expensive - both in initial cost and in the replacement of pricey, shorter-lived projector bulbs - plus contrast can be an issue in a dark room. But for permanently installed systems demanding extremely high quality projection, the investment may well be worthwhile.

CRT projectors (cathode ray tube)

Cathode Ray Tube projectors use the same technology as traditional televisions and computer monitors. They are analog, rather than digital, using separate red, blue and green tubes or “guns.” Large, heavy and expensive, CRT projection systems are most at home in a fixed installation, and have been a favorite in auditoriums and bars (they are also less susceptible to smoke damage than the average digital projector). The need for regular professional calibration is a turn off for some people, but the image quality and technology have a long and successful track record.

Although each projection display system technology has its advantages and weak points, identifying the best choice is partly a matter of personal taste. For that reason it’s a good idea to get out and compare what the different systems look like with your own eyes, so you can judge what projector technology is right for you. If that’s not possible (projector demos are few and far between) understanding the options is your best weapon.