P3D Stereo Laser Pointer

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

When I read Ron Labbe's original post about a stereo
laser pointer I immediately saw his "point" of pointing
things out in 3-D space. Great idea!!!

Anyways, after reading all the posts I thought to my
self, it's time to get off the computer and actually
see if all these theories, posts, etc. were true! ;-)

However I wasn't up to crawling into the attic to get
out the musty, dusty ole TDC 116 projector or looking
for the projection screen, so I just went to the 
kitchen instead and got some Aluminum wrapping paper.
I got two of my numerous laser pointers (cat loves 'em)
and 3-D glasses (non-anaglyph of course!). 

Okay now came the big moment..., I went into another
room (with cat following me of course, she knows when a 
laser show is coming up) and turned off the lights. I
stuck the Aluminum paper on the wall with some tape. I
put on the 3-D glasses and pointed the laser pointers
on the Al paper. Gingerly rotating the two laser
pointers, I determined where the spots were the darkest
and brightest for the corresponding eyes.

Now came the moment of truth. I varied the spacing of the
spots on the screen (Al paper) and could faintly see the
spot recede into the wall! Superimposing them of course
made it come back to the screen. I couldn't determine if
they came off the screen by diverging them more, because
there was a bit too much ghosting. In any case my hands
were getting tired from holding the lasers in awkward
positions and continuously applying pressure on those
blasted momentary ON switches.

The beam being very bright, I thought maybe putting those 
diffraction gratings that you put in front of the pointers
to get different shapes, messages, etc., might help. This
time I taped the ON buttons and shining a "happy face" on
the wall, the 3-D effect was much more pronounced and ghosting
much reduced. The intensity was somewhat reduced but still
bright enough. Again, by simply varying the overlap of the
"happy face" I could adjust it in 3-D space and off the
screen. 

Next time I'll have to fire up the TDC and see how well
it stacks up in projection. I'm guessing, simply shining
the red spots should be okay (ghosting wise), since the
projection should reduce any ghosting. Also the screen will
have better polarization. After all this, I can see how
a 3-D pointer would be a useful and fun thing to have!!!

P.S. I don't know what other applications Larry was thinking
of, but how about using this principal to project stereo
laser shows instead of the regular 2-D kind? Has it been
done?

Gabriel



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