Re: Laser pointers

[P3D KENNETH LUKER <KLUKER@xxxxxxxxxxxxxxxxxxxxxxx>]

> pointers are polarized. So wouldn't it be fun to split the beam 
> into two, orthogonally polarized beams and then, by adjusting the 
> separation of the spots on the screen , you could actually point out 
> something in three dimensions!! I'll give it a try and report 
> back.

I've regularly used a laser pointer during my shows.  The un-
polarised laser dot seems to float right at the surface of the
window, which, if the edges of the slide are matching, is right at
the surface of the screen.  I've noticed, though, that I can make
the dot sink into the surface or come back away from the window if I
adjust the horizontal separation of the two images.  This plays
havoc with the eyes of the observers if it's done very much, because
the viewers' vergence changes as the images shift in separation, but
it is VERY effective if you want to put the dot precisely on a point
within the picture.  What is happening, of course, is that the laser
is on the screen, and it appears to be at the same z-axis location
as are the points of the image that also exactly coincide on the
screen.  Move the images so the infinity points are at the same spot
on the screen, and the laser dot will appear to be at infinity. 
Don't do this very much if you want your viewers to come back, but
it is fun as a trick. 

Ken Luker
_______________________________________________________________

Kenneth Luker, Assistant Director
Systems and Technical Services
Marriott Library
University of Utah
Salt Lake City, Utah
KLUKER@xxxxxxxxxxxxxxxxxxxxxxx


------------------------------