I was over at a friends house and he had a broken projector that he had pulled from a dumpster, we of course started to disassemble the device.
It became immediately clear that it was abandoned because of a broken bulb. While some LED projectors are now on the market, the majority still are and have been based on a big honkin' bulb to project an image. The big disadvantage is that an incandescent bulb is typically used, which puts out a lot of heat and eventually burns out.
These bulbs are then very expensive to replace, and as projectors get cheaper, it is often easier to buy a new projector than to replace a bulb on a previous generation model.
From the projector I pulled out a whole bunch of goodies for use in future projects. Lots of centrifugal fans, used here for their small form factor, and usable in many projects. There were also two AC to DC converters, one for the electronics in the projector, and one just for the bulb. The different optics in the device were also pretty cool, with some polarized lenses each filtered for red green or blue.
The most important piece (for this instructable) is the actual lens of the projector.
Step 1: Brainstorm!
The most important thing here is figuring out the relations between the different parts, and what needs to be mounted where compared to everything else. The dimensions of the flashlight and lens assembly are the ones that I took in the previous step.