[photo-3d] Re: Nu-View as Video Beamsplitter

[Jim Crowell <jcrowell@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

> from:
> Ian P. Howard, Brian J. Rogers "Binocular Vision
> and Stereopsis" New York and Oxford 1995, page 398,
> 
> which shows the zone of clear single binocular vision.
> The figure was adapted from:
> G.A. Fry (1939) "Further experiments on the accommodation-
> convergence relationship" Amer J of Optometry, vol 16, pp
> 325-334.
> 
>> From the figure you can read for example that with one diopter
> of accommodation (looking at one meter distance) convergence
> is possible from zero (infinity) to about 10 degrees (about 40
> cm or 15 inch distance, with 65 mm interpupillary).
> This might give an idea about the elasticity of the AC-link!
> Compared to this bungy jumping is nothing...
> 
> Abram Klooswyk
> 
 
I think perhaps "link" is too strong a term.  "Tendency" might be better;
when their eyes are accommodating to a given distance, most people have a
tendency to converge at a particular distance (which may or may not be the
same as the distance they are accommodating to; people who tend to
overconverge are referred to as esophores, those who tend to underconverge
as exophores).  Converging at other distances than the preferred one is
believed to require some effort and, if excessive or maintained over an
extended period of time, may lead to eyestrain; phoria measurement is
becoming a fairly common component of eye exams.

That said, I've never gotten eyestrain from a viewer, but have gotten severe
headaches (as someone else said) from some of the earlier IMAX movies.
"Into the deep" was particularly bad, as it required quite near convergence
for a good part of the movie.  The more recent ones seem to be a lot better
in that regard.

-Jim C.

-------------------------------------
Jim Crowell, Ph.D.
Dept. of Psychology
Cognitive/Experimental Group
Townshend Hall
1885 Neil Ave. Mall
Ohio State University
Columbus, OH 43210
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