P3D Re: stereo laser pointer

["KENNETH LUKER" <kluker@xxxxxxxxxxxxxxxxx>]

> >I have to ask: just what makes a laser pointer stereo or flat?
> >Please forgive my ignorance and inexperience.
> 
> I have no patience with any of these two "defects" but will still
> try and answer... If you can control the depth with respect to
> the screen that the point is pointing, then you have a stereo
> pointer.  Otherwise it is flat.

Although it might cause some inconvenience to some viewers, there is 
a way to have a laser pointer zoom into and out of a projected stereo 
view without doing anything special with the laser.  The laser dot 
falls on the screen, and therefore appears to be at the z distance 
intersected by the screen.  By adjusting the separation of the 
lenses, and hence of the projected images, you can move the placement 
of that intersection.  By lining up the infinity points to coincide 
on the screen, the laser point appears to be at infinity.  By 
separating the images so that infinity recedes behind the screen, the 
laser dot appears to approach the audience.  When the  adjustment of 
separation brings the edges of the projected images to coincide on 
the screen, the laser dot appears to be at the stereo window.  Etc, 
etc.  

I've done this by standing at the projector, pointing the laser with
one hand and adjusting the separation with the other.  Since folks
are usually looking at the laser dot at the time, their eyes are not
twisted (they're converging at the screen distance) and the
discomfort is minimal.   To point to a particular feature, bring 
the homologous images of that point together on the screen, and 
touch them with the laser. The effect is dramatic. 

If you look at a point in the picture while this adjustment is being
done, you have the distinct impression of seeing a red dot receding
and approaching in real space.  It's best to do the adjusting 
smoothly, and usually with a single twist of the adjustment, you can 
bring the dot from infinity to the window in one smooth motion.

Ken Luker
_______________________________________________________________
Kenneth Luker
Marriott Library Systems and Technical Services
KLUKER@xxxxxxxxxxxxxxxx


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