P3D Re: VM and Kids

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

Gabriel Jacob writes:
> Bruce Springsteen writes:
> >If I read my Ferwerda right, 2 simple convex lenses of a given size,
> >set in a stereoscope with their principal axes (centers) at an
> >interocular separation matching the infinity separation of the
> >stereoview, will allow an unimpeded view of left and right frames for
> >persons whose eyes are within a *range* of interpupillary
separations.
> >What is this range?
> 
> The range depends on the diameter of the lenses.

Exactly!  In the case of VM the "lenses of a given size" are fairly
small. So rather than discussing interoculars, and the adjustment
thereof, maybe larger diameter lenses is the answer to making VM
viewers more kiddie-friendly.  What the limit of that solution may be,
I dont know.  What say you?
> 
> >One last thing.  I believe adding an interocular adjustment to VM,
> >while retaining the same infinity spacing on the views, would make
> >the wee ones diverge - and that hurts, mommy!
> 
> True. As George mentions, theoretically it should be fixed but most
> users prefer (myself included) adjustable interoculars. Another
> option (expensive) is to use prisms or mirrors.

I like adjustable too (ie: on the Red Button), but that's a different
situation.  With my 70mm eye spacing, I'm moving the lenses *out* so I
can converge slightly, for more comfort.  Moving the lenses *in*,
creating ouchy divergence, is a different matter.  And I think both
adjustments introduce image distortions.

> Last years talking VM has a slightly reduced lens spacing (~62mm)
> but might be immaterial since the quality is awful.

Yeah, especially for people with jumbo heads like mine! ;-)  Are the
lenses fairly large?

Happy NSA.  Toast your absent friends!
Bruce.
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