P3D Projector Autofocus

[Tom Hubin <thubin@xxxxxxxxx>]

Hello,

My understanding of projector autofocus is that a spot, probably
infrared, is focused onto the slide from the screen side. Then the
projection lens is focused manually. Then the system stays in focus by
moving the reflected spot into a consistant location. I can envision how
this would work.

If you use cover glass then there will be two reflections, one from each
surface of the glass. This probably does not matter as long as all cover
glass is the same thickness and has the same index of refraction. I am
willing to ignore the index variation as it is likely to be very small. 

But what happens if your slides are mounted with a variety of cover
glass thicknesses, including the special case of zero thickness for no
cover glass. Do you need to manually focus whenever the cover glass
thickness changes? 

Any good tutorials on projector autofocus methods and their limitations?

Are there any stereo projectors with autofocus?

Tom Hubin
thubin@xxxxxxxxx


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