photo of dmd and hand

What is DLP® (Digital Light Processing)?

Digital Light Processing (DLP) is a display technology developed in 1987 by Texas Instruments. It is based on an optical technology that uses a digital micromirror device (DMD), and is a set of chipsets with different performance characteristics.

Larry Hornbeck of Texas Instruments was the inventor of the system, and found its way into the first digital projectors in 1997. Today, DLP is the most used imaging device in the digital projection market and the preferred solution for many applications that require the benefits of the system.

What is a digital micromirror device (DMD)?

One of the key components in the DLP technology is the DMD. This is the component that creates the individual pixels, and the total image is created by microscopically small mirrors placed in a matrix on the DMD semiconductor chip.

Each mirror represents one or more (using wobulation/pixel-shift technology) pixels in the projected image, and the mirrors on the DMD are so small that the DMD pixel pitch (the distance between pixels) may be 5.4 µm or less.

Digital Micromirror Device (DMD) from Texas Instruments

Photo of a DMD from Texas Instruments.

Photo of the actual mirrors on the DMD chip

How does the small mirror size influence the optical design?

Because of the small size of the individual pixels, the optical design of the projector is a crucial factor when it comes to image quality. If the optical resolution on the lens does not match the size of the pixel, the image will be experienced blurier and important, fine details in the image might be lost. When selecting a projector manufacturer for any installation, it is important to check if their lenses are designed for the high resolution or if they are re-using lenses from older designs with larger DMD mirrors.

How does DLP work in practice?

There are two different approaches to designing a projector with a DLP system: One-chip and Three-Chip. In a one-chip system, there is only one DMD to create the image and traditionally you needed a color-wheel to create the different colors. In a Three-chip system, you have one DMD for each of the primary colors, red, green and blue. 

The downside of a single-chip system is the color-wheel as it creates the colors sequentially on the screen and not simultaneously as with a three-chip system. This is often referred to as the rainbow effect and causes bad artefacts in the image (looking like rainbows obviously). 

The benefits of a single-chip system is the price, reduced design complexity and size – building a three-chip system results in bigger projectors. 

With the introduction of solid state light sources in projectors, the rainbow effect has been eliminated because there is no longer a need for a colour wheel in the projector to create the colors.

What are the benefits of using DLP/DMD in projection?

First of all, the DMD is a semiconductor that is built completely with inorganic materials. This has a great impact on the longevity of the device. From the manufacturer’s data, the device has a Mtbf (Mean time between failures) of up to 150,000 hours. Secondly, the DMD is possible to seal in a way that makes it impossible to get dust and small particles in the optical design, that will normally reduce image quality drastically. Additionally, DLP projection systems provide excellent contrast and image brightness uniformity, which also are important factors in many high-end projection installations, such as simulators, planetariums, scientific visualization, control rooms and other use cases.

If you are interested in other important factors to consider when selecting a projector for your simulation system, have a look at our free Checklist if you want to see all.

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