P3D Mirror stereoscopes

[abram klooswyk <abram.klooswyk@xxxxxx>]

David Lee wrote (P3D 3716, 11 Feb 2000, Re: New 3D Site): 
>(...)
>I have shown cards with Keystone viewers on stands 
>(I have 9 of them), but usually I make large (10"x10")
>prints and use large viewers which I invented and manufacture 
>for that purpose.

In an informative article at: 
http://www.berezin.com/3d/Article.html
he adds:
>(...) The principles used in this viewer are not new. 
>Both aerial stereo viewers and X-ray stereo viewers are 
>similar in concept. 

I like the views on the sites David refers to.
Just as an historical note, the first to have added a second pair 
of mirrors to the Wheatstone stereoscope seems to have been 
Hermann [von] Helmholtz, in his Telestereoskop (1857). 
This was for real-life hyperstereo viewing and had binoculars to it.
The design for viewing of stereo images (adopted by David Lee)
was first used by the Frenchman L. Cazes around 1890.
The X-ray stereo viewers mentioned have been manufactured till
some thirty years ago, I suppose. They could be used for X-rays 
up to 14" x 17".

Abram Klooswyk