Display Tech: Home Projectors

We all love our home TVs, but whether they're LCD or Plasma screens, some people believe that the absolute best way to enjoy films and movies at home is to use a projector. Theatres and Cinemas around the world use huge film and digital projectors, so why not have one at home? Today we're explaining two types of at-home front projector technologies and how they work.

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Similar to the traditional flat-screen TV game, the home projector game consists of two types of technologies: LCD and DLP. Short for Liquid-Crystal Display, LCD projectors are a cousin of their Television brethren. DLP, short for Digital Light Projection, is a brand of projector technology that uses a Digital Micromirror Device (DMD).

A DMD is actually about the size of a microchip, and consists of thousands of tiny computer-controlled mirrors. Each tiny mirror on the chip represents one pixel on screen. Like all things digital, these mirrors can be turned on and off by adjusting the angle of the mirror on the chip towards the projector lens, or away from it.

The other major part of a DLP projector is the Color Filter, or Color Wheel. This fast spinning wheel has translucent red, green, and blue sections, that together with the DMD forms a moving image. From the light source, light travels through a "condensing lens" to focus it as it travels through the color wheel, back out through a "shaping lens", which then focuses it on the DMD. The DMD then reflects the image out the projector lens and onto your silver screen.

DLP diagram by Cameron Christopher

LCD projectors work similarly to old-school slide projectors. These projectors incorporate small translucent LCD panels, which work just like those in large flat-panel TVs. White light is emitted from the light source, and is split up into three parts by "separation prisms". These three light beams each pass through a separate red, green, and blu filter, and then through their own tiny LCD panels. From there, the three beams go through "combining prisms" which - surprise! - combine them into one light beam before going out the optical lens and onto your projector screen.

LCD projector diagram by Cameron Christopher

Compared to LCD projectors, DLP tends to have smoother video, with a higher contrast ratio, "blacker" blacks, and a more film-like and cinematic feel. Additionally, if space is an issue, DLP projectors are physically smaller. On the downside, some older DLP projectors may suffer from the so-called "rainbow effect" where the edges of brightly lit moving objects may appear as red-green-blue ghosts instead of white. DLP also tends to run hotter, and due to the spinning color wheel, may make a noticeable whine or hum when in use.

On the flip side, LCD projectors run cooler and quieter than DLP, and can produce a brighter image when placed in a room with a lot of ambient light. However, these projectors don't have the same contrast ratio as DLP, with blacks appearing to be more grey. Also, some LCDs can produce a "screen-door" effect, making images appear blocky with small spaces between pixels.

Both DLP and LCD projectors measure their light output in lumens. Generally speaking, the higher the lumens, the brighter your picture. However, a brighter picture doesn't necessarily mean a higher quality picture! Additionally, while a projector can spit out 2,000 lumens, other considerations must be taken into account, such as room size, screen size, screen material and reflectivity, and perhaps most importantly, ambient light. The more ambient light in your home theatre, the more light needed to project light onto the screen. Most home theatre projectors range from 1500-3000 lumens, depending on your application.

Armed with the basics of home projectors, the time has arrived to light up your living room with all your favorite Couch Mode likes. Happy watching!