The theory behind projection:
The principals that make projection in general possible are very simple in concept. You need simply 4 requirements to be met: a light source, the brighter the better; some form of imagery medium, film or LCD it's all the same conceptually; a focusing mechanism to help provide a crisp image; and finally a display medium. There are many ways of accomplishing each of these requirements. We will be glancing over them and providing some examples that could fulfill the requirements for our LCD Projector.

The Light Source - The LCD Projector Bulb
Back in the day traditional carbon arc were used in actual film based projection, but modern xenon arc lights are now more common. Xenon's were introduced in the 1950s, they are safe and easy to use, and are relatively cheap. Most all LCD based projection use Xenon or filtered Metal Halide, based light sources. Commercial or non DIY projectors can have bulbs that are very very expensive, often in excess of $500.00 for a bulb that usually can only last for 2000 hours. All bulbs are sensitive to shock, getting bumped too hard can be a costly mistake. So what are the most common practical light sources?

Xenon Light Source

$20 - $150

Construction Utility Lights

$50 - $250

Modified Automotive Head Lights

$10 - $40

Overhead Projectors

$10 - $150

Coustom Solution

$20 - $100

The Imagery Medium - The LCD Projector Panel
Historically, cellulous based films were used as the imagery medium. Light passing threw the film, and interacting with a shutter created the viewable content. LCD projectors act on a similar principle. Light passing threw the LCD creates the viewable content. There are many ways of using LCD's of many verities. Now, here is where I have to return to the point that this may not be the first how-to article. There are a lot of articles with little to no foresight in this type of project. Picking a cheap LCD monitor off the shelf for instance is a bad idea. Normal LCD (Liquid Crystal Display) are not designed to be used in high-heat environments. Using a cheap LCD panels can result in nothing more than an expensive paperweight. The seal around the edge of the monitor can crack or become damaged allowing the liquid layer between the layers of glass to dry out and become worthless. Secondly, there are many DIY attempts to fulfill the requirements of an inexpensive monitor with a small (4 inch or so) LCD panel. The problem with this is most small monitors have only 250 or so lines, so you may as well throw the image quality out the window. These methods do work, they just are not very effective compared to similarly priced solutions.

15" LCD Monitor

$170 - $250

5 - 6 " LCD Monitor (without svga support)

$70 - $130

5 - 6 " LCD Monitor (with svga support)

$180 - $270

LCD Projection Pannel

$20 - $90
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