I happen to have in the basement a 3M 9550 overhead projector with a working bulb and a 15" LCD screen (now taken apart). Since I like to play Visual Pinball I am wondering if I can build a projector that will project an image downward from the ceiling (presumably) onto a "table". I have never built a projector but am worried about the short distance I have have to work with in the unfinished basement. The distance from the bottom edge of the floor joists from the floor above to the table is just 50 inches. I ran a test and it looks like the projector will focus at exactly that distance, but no less. The spec sheet says is has a Varifocal 280 mm to 320 mm (11" to 12.6") lens. I'm not really sure what that means. But my problem will come when I build the projector and probably eat up a few more inches with the case. Anyway, I thought I would just post this here to see if this is a good or bad idea etc. I already own the parts and I have tools. Also I am wondering about the ability to project the image at an angle (so light would come from a few feet distant from directly overhead (to avoid my shadow). Can I correct for that with the lens? The final result will be a method of playing hundreds of virtual pinball "tables" on a screen that will have some mechanics for the buttons and nudging and so on. I'm ready to start on the project so I would appreciate any advise. This is also meant to be something of an experiment where I learn about optics.
You would have to adjust the vertical angles of the fresnel lens to get some sort of keystone correction. That would allow you to put the projector above your position.
I would make the surface perfectly perpendicular to the throw from the projector.
I would make the surface perfectly perpendicular to the throw from the projector.
Hmmm - I think I was assuming that keystoning would be required to avoid a player casting a shadow on the table. I think my real problem is insufficient distance between my low ceiling and the table. Maybe that would mean getting a different lens? Maybe from an old projector TV?
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