P3D Re: Hugo de Wijs VM viewer, Re: Normal interocular spacing?

[abram klooswyk <abram.klooswyk@xxxxxx>]

(Continued from P3D Digest 3222, 02 Mar 1999)

In 1895 L. Cazes wrote a little but interesting book:
"StÈrÈoscopie de PrÈcision" (Michelet, Paris 1895)
I will discuss some of his ideas later, now I only quote how he 
described his symbol for interpupillary distance "delta" (he used
the Greek character):
"l'intervalle des yeux que nous Èvoluerons en moyenne ý 6 cent. en
France et ý 7 cent. en Angleterre", which means something like:
"the separation of the eyes which we found at a mean of 6 cm in
France and 7 cm in England".
There is no indication of the source of these figures, which most
probably where both not very PrÈcise, but which obviously meant
an average of 65 mm in the Channel.
Most funny is of course that giving figures for only England and 
France apparently was sufficient.

>From the stereoscope scheme I tried to draw in P3D Digest 3222 is
clear that the separation of the lenses should be adjusted to the 
images (to the far point separation of them), and not to the observer.
It also is clear that then the usable diameter of the stereoscope lenses 
will limit the number of people which can use that stereoscope.
It follows that, when you want a stereoscope to suit a maximum number 
of people, you must choose a standard infinity or far point separation
for the stereo picture which is close to the mean of the 
interpupillary distances of the people you aim at.

For example, a far point separation of 65 mm requires a stereoscope
lens separation of also 65 mm. Then lenses with a usable diameter of
10 mm will suit people with interpupillary distances from 55 to 75 mm.

Suppose you want your stereosystem to be used not only in England and 
France, what is the mean interpupillary of your customers?

(to be continued)

Abram Klooswyk


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