P3D Re: Viewing with vs. without lenses

[Tom Hubin <thubin@xxxxxxxxx>]

Mr.Lizard wrote:

>     The new View Master Virtual viewer looks cool, but does not help me,
> since my glasses get in the way.  The older viewers are no different.

If the eyeglass frames are too large for the viewer then a second pair
of eyeglasses with a small frame might be helpful. If this is the case,
take a viewer with you to your optician so you can test the eyeglass
frames for clearance.

If the lenses are in the way then their is not enough eye relief
designed into the viewer. This is a common difference between cheap and
expensive binoculars. The expensive ones have the exit pupil maybe 14 mm
outside the eyepiece lens. Your eye pupil would easily match this
position. Without glasses there is usually an eyecup so that your eye is
far enough away from the eyepiece. With glasses on you remove or
collapse the eyecup.

Cheap binoculars have the exit pupil at or very near the eyepiece lens.
So you need to get your eyeball close to the binocular eyepiece lens. If
you cannot get your eye close then it looks like you are looking through
a 4mm to 7mm diameter tunnel that is 10mm to 14mm from your eye.

So you may need to shop for viewers with enough eye relief. This is
often specified in optical systems like binoculars. I doubt that it is
specified for viewers. But I am guessing.

Another alternative is a stereo relay lens system that reimages the exit
pupil someplace where your eye can get to it. I'll think about that a
little. The tricky part will be avoiding inverting the images. 

Tom Hubin
thubin@xxxxxxxxx