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What are LCD Projectors?

J. Dellaporta
J. Dellaporta

LCD projectors are systems that display or project information or video onto a surface. LCD stands for liquid crystal display, the technology used to project images. They are the technological descendants of overhead and slide projectors, older systems which serve the same purpose. They are most commonly used for displaying images in presentations or lectures, but are also used in home theaters.

Video signals are comprised of three colors: red, green, and blue. LCD projectors contain a separate glass panel for each. Each panel consists of two plates of glass with a layer of liquid crystal between them. When a charge is applied, the crystals open to allow light through or close to block it. This opening and closing of pixels is what forms the image.

Video signals are comprised of three colors: red, green, and blue, and LCD projectors contain a separate glass panel for each.
Video signals are comprised of three colors: red, green, and blue, and LCD projectors contain a separate glass panel for each.

These devices use dichroic mirrors to split the light from the input source into red, green, and blue components. Each then passes through the corresponding panel, where pixels form an image. The three colors are then recombined in a prism before being projected through a lens. LCD projectors use separate panels for each color because it results in better color saturation than using a single panel for all three.

While all LCD projectors perform the same fundamental task, there are many different models available, and consumers should know what their projector will be used for before selecting one. These devices are priced based on several factors, especially resolution. The highest resolution ones are only worth the money for those who need to project fine details as accurately as possible. The right amount of brightness, measured in lumens, depends on the lighting conditions the projector will be used under, as well as audience size. A darkened home theater requires less brightness than a fully lit conference room.

Other factors in considering LCD projectors are portability, computer connectivity, and input options. Those with higher resolution weigh more and are therefore less portable. Those using multiple computers to make presentations should consider a projector that is easily compatible with different systems. Projectors used to show movies in a home theater should have component video inputs for the best picture quality.

LCD projectors are frequently compared to digital light processing (DLP) projectors. These use circuit boards with thousands of tiny mirrors to project an image. Their chief advantages over LCD projectors include smaller size because they do not use multiple LCD panels, better color contrast, and no pixelation effect like that sometimes seen on LCD devices. However, LCD projectors are still known for having better color saturation. Generally, DLP is more popular for home theater use.

Discussion Comments


@jmc88 - Finding a portable LCD projector with all of those features you need might be difficult but not impossible. I was given the job of buying all new projectors for our building a couple years ago, so I assume a lot of the information from then is still relevant.

First off, I am assuming you have some sort of a cart or something for the projector if you need to take it from room to room. The type you are looking for can get quite heavy, and it isn't a good idea to jostle them around by carrying, either. Not to mention you avoid dropping them that with the cart.

I don't have any experience with DLP, but I think you could do fine with the regular LCD. Panasonic LCD projectors are good for what you need. I would suggest trying to find something with at least 2000 lumens, since you'll also be using it in conference environments.


I am looking into buying a new LCD multimedia projector for our office. The one we have right now is pretty outdated and doesn't have a very good picture to it.

One of the issues we have is that we watch a lot of movies as part of the job, so it is important to have a projector that gives good quality. Besides needing to watch movies, most of everything else we use the projector for is slideshows. The other consideration is that we have a couple of different rooms that the projector is needed in, so it should be portable, as well.

Does anyone have any experience buying movie projectors? I wasn't familiar with DLP before reading this. Would that be a good choice?


@Izzy78 - I think your guess is correct. The projectors have the ability to control the light levels of the three colors for each of the pixels that will be projected. How much of each color is let through the filter and into the final image will determine what colors show up on the screen.

As with all other electronic screens, pixels and resolution are linked to each other. In other words you get higher resolution with more pixels, because there is the possibility for less abrupt changes between different colors on the screen.

I don't know who came up with the idea of how to make an LCD screen, but it seems like there is a lot of stuff going on inside of the projector that makes a final picture.


I always wondered how LCD devices worked. Now I guess I know. What I am still not quite clear about is how exactly you get from the red, green, and blue to all of the different colors that are displayed on a screen.

I understand that it starts out and white light is divided into the three colors. How are those then projected back through the prism onto the screen? I guess my real question is how all of the pixels are made. Are there tiny little "screens" inside of the projector that open and close to let light of the different colors through for that individual pixel? It seems like that is almost how it would have to work.

If you didn't divide the final projection up into the different pixels, there would be no way to mix the colors of light and you would just end up with a white picture.

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    • Video signals are comprised of three colors: red, green, and blue, and LCD projectors contain a separate glass panel for each.
      By: nicolasjoseschirado
      Video signals are comprised of three colors: red, green, and blue, and LCD projectors contain a separate glass panel for each.