Talk:Multitouch screen

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I think you will actually need a convex mirror for this setup. A concave mirror will only require MORE distance to get the image to the right size since the rays have to converge and then rediverge. Try tracing several rays from the projector to the screen using the mirror and an estimated reflection angle. With a concave mirror, there will be a point after the reflection where all the rays converge where with the convex mirror, they will never converge. The only way a concave mirror will work is if it has a REALLY small focal length. -Kinsey

Perhaps you're correct. I was working off the only setup I've seen using an external mirror, and I believe it used a concave mirror to project onto a screen placed above the projector itself. I'll look into this some more and probably take some more notes. --strages 16:49, 17 April 2007 (CDT)

Deeper the mirror the shorter the focal length correct? --strages 05:46, 18 April 2007 (CDT)

Yes, a deeper mirror is more curved and will converge the light more quickly (shorter focal length). This also applies to convex mirrors. --Opticron 07:07, 18 April 2007 (CDT)

Instructables Link to building Multitouch. --JimShoe 11:02, 12 July 2007 (CDT)