Projectors are used throughout the world and are often used for some pretty cool things. It is always exciting to watch a movie on the big screen, set up a party in a place with no tv, or simply make hand puppets in the beam of the projector. What isn’t often thought about though, is how the projectors work. In this blog I will cover the engineering behind the DLP category of projectors since they are generally the most common and most affordable. Other categories include LCD projectors, laser projectors, LED projectors, and LCOS projectors, but I won’t be covering those types in this blog.

To begin, let’s cover the basics of how any projector works. A projector consists of a lamp, a pixel manipulation system, a zoom lens, and a focal lens. The light from a projector is created by the lamp system. These lamps are generally incredibly bright and energy intensive, often ranging from 2,000 to 4,000 lumens and drawing anywhere from 150 to 800 watts an hour. These lamps need to be as strong as they are because all of the light is distributed across the viewing area. The larger the screen, the dimmer the image, so bright lamps are needed. Next, the light passes through a pixel manipulation system. This system is where color is added and pixels are created from the unified light beam. In this blog, I will cover the DLP pixel manipulation system. Finally, the light is focused and zoomed through a series of glass lenses like those found in a camera lens.

Now onto how a DLP projector works. Similarly to before, a lamp shines light into a pixel manipulation system. In this case, it consists of an RGB color wheel and a device called a “digital micromirror device” or DMD for short. After the light is created, color needs to be added to the image, so the light is passed through a color wheel. The wheel spins at a high rate so that the colors all blend together. Once every 1/50 of a second, a human eye blends together all of the color it sees, forming an image. The DLP projector wheel spins so fast that the human eye doesn’t realize that only one color is being displayed at a time. Once color is added to the light, it needs to be broken up into pixels. This is the job of the DMD. The digital micromirror device consists of thousands of incredibly small mirrors, or one for every pixel. These mirrors all have a hinge on them that allows them to tilt the light towards the focusing lenses or towards the inside wall of the projector. When it is time for the projector to create an image, the mirrors direct light for pixels that are “on” and divert the light for pixels that are “off.” This process in combination, with the color wheel, is able to provide a sharp image that is full of color. After that, the light is focused in the focal lenses, and an image is displayed.

It’s as simple as that! The idea of a projector is incredibly simple, but the actual process is quite intricate and complicated. Next time you watch a movie, try to appreciate the machinery that goes into making it all happen!