A projector made from a salvaged LCD monitor, some optics and a really bright light. I made this sometime during the summer of 2007 after stumbling upon an online community dedicated to building high quality projectors. High quality you say? Most projectors back then were 640×480 or 800×600 native resolution and cost quite a bit. In addition to the cost, the halogen lamps had a very limited life, usually 50-200 hours, and cost an exorbitant amount to replace. The projector I built had a 1280×1024 native resolution.
So how does it work? The LCD monitor you are most likely looking at is a actually very transparent. There is a light of some kind illuminating your panel from behind. The light passes through some optics to evenly distribute it throughout the panel, and passes through the transparent LCD to produce the colors that you see. Armed with this knowledge, making a projector from a regular computer LCD monitor is possible. But there are drawbacks, of course. Most important drawback is size – commercial projectors are fairly small because they employ very small, pixel dense LCD’s which is why they were expensive. If you didn’t care about the size, next problem is heat dissipation. Running a large lamp is going to generate a fair bit of heat.
With all this in mind, should you choose to go forward, then here is the way. Some things you’ll need are:
1. Computer LCD monitor, which you will strip of it’s housing so that you only have the clear LCD and it’s associated electronics
2. Materials to make the projector housing out of
3. Fresnel Lenses (they will be polycarbonate), 2 of them of differing focal lengths suited to your needs
4. Projection triplet lens, focal length based on need
5. 400W or more metal halide lamp and holder
6. Material to create a reflector for the light
7. Ballast and electronics/wiring to power the lamp
8. Fan and electronics to keep things cool
9. Glass plate to prevent the fresnel lenses and LCD from melting
Armed with all this, you may go. The operation is fairly simple: You provide a large light source with a reflector at the back of your projector housing. Next, you put a glass plate in front of the light and reflector, as the light will be generating massive amounts of heat which is liable to melt your fresnel lens and your LCD panel. After that, you provide a fresnel lens at the right distance based on your focal length. The purpose of this fresnel lens is to collect all the light and make them straight polarized light (This lens is usually called the collimator). Next up is the LCD monitor, which is transparent, followed by the other fresnel lens. This second fresnel lens works in reverse of the first one — it’s job is to take the light that passes through the LCD and focus it all into a small area for your projection triplet. Finally, the projection triplet will take this light and project it onto the wall.
Taking things apart to build new things is quite fun, but even more so when you have a friend! I had ordered an electronic ballast for my lamps after buying a cap and coil ballast and realizing it was really ugly. I also had ordered two sets of lenses and optics in case I screwed up, so I invited a friend to build a projector with me in parallel, provided he could get an LCD monitor. I am happy to report that he did, and it was a blast. Especially interesting is how our designs were both different aesthetically. I chose to make my enclosure an ugly 3d rectangle, my friend chose to give his a nicer shape. Form over function? You be the judge.