A very interesting project, I'd like to try one of those projectors someday.
Here's a link to the
DIY Projector Company website. Lots of free information and theory. They've got some designs with mirrors to turn the light path in the projector to make the box smaller.
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killernoodle writes:
The focal point of a sphere is the very center, so if you put the bulb part in the very middle of the sphere the light will bounce off of the reflector and back into the bulb.
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It seems like a spherical reflector is recommended by most of the projector builders and parts vendors, but I have my doubts if it's the best, or even a good answer. You want to avoid having the light directed back to the arc tube to keep it from overheating. I've seen metal halide lamps after they've been operating in a poorly designed reflector that focused too much light and heat back at the lamp. In some the arc tube had bent, and in others the arc tube had bubbled before failing.
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JWFokker adds:
I understand why the current system works with a point light source, but there's got to be a way to use a parabolic reflector to achieve a more even distribution of light. I had something along the lines of a spotlight, which is why I was looking at photographic reflectors.
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I think you're on the right track.
killernoodle-I haven't seen a picture of your lamp. Was wondering what the diameter is. That lamp and ballast in a box are going to put out a lot of heat. If you've got a T-15 or ED-18 lamp, google for 'pyrex cooltube'. It's a pyrex bread baking tube about 4" in diameter x 12" long that these lamps will fit into. They're used by indoor gardeners with the same lamps and a similar heat problem.
Get some airflow through the tube, over the lamp, and out of the box and it might help keep some heat off your LCD panel.