Re:3D images using Black Barrier Strip

[P3D Jeremy Hinton <Jeremy.Hinton@xxxxxxxxxxxxx>]

Tom/Gecko wrote:

> I'd like to get more information on creating
>3D images using the "black barrier strip" method.  
>If I'm correct, it creates a 3D image
>similar to that of lenticular.

>Any info would be helpful.

Seeing as no other responses have turned up yet...

Your description sounds like the 'Parallax Barrier'or 'Parallax 
Stereogram' Method.
I believe it is covered in a series of patents by Frederick E. 
Ives, between 1902 and 1905.  


Some years ago I made some examples by interleaving stereo 
images (grabbed sequentially from a video camera, because that 
was the technology available to me at the time) and printed on 
a laser printer. I used a sheet of 0.25 inch (approx) perspex 
as a spacer, and laser printed the parallax barrier on clear 
acetate. That was the tricky bit, getting the barrier spacing 
ever so slightly less than the pixel spacing on the paper 
(because the parallax barrier is a fraction closer, and it 
must have the same spatial frequency at the eye). The arithmetic 
(can't call it math.) is very straighforward, but the printer only 
prints whole dot-widths.   

It worked OK. Proof of principle, but I only had a standard B/W 
laser printer for both image and barrier. (I could have made the 
image by photographic enlarging through the barrier, analogous to 
the way Nimslo prints through the lenticular screen). A red-button 
viewer would be better even with flat batteries. One thing I wanted 
to do was to make the barrier lines opaque but _not_ black (light 
grey). Then the barrier would not itself be resolvable at reasonable 
viewing distances. I still can't think how to achieve that with 
sufficient accuracy.

Finally I made some barriers to fit in front of LCD displays. 
Specifically a Mac Powerbook. Now _that_ worked a treat. I 
suspect that the backlighting and colour improved the effect. 
The main trouble is that lenticular overlays are better.


Jeremy  (fresh from the Stereoscopic Society Convention.... 
        most notable for meeting a fine bunch of names from 
        this list in the flesh. Good to meet you folks).


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