This little gizmo is used to view stereoscopic images on a postcard-sized printout. The centers of the two images should be 64mm apart for optimal results (that's the interpupillary distance this was designed for). The lenses I used were 35.5mm in diameter
Only one place needs glue: the interface between the viewer and the slider. Align the bottom edge of the viewer with the curve of the slider (make sure it's centered) and use strong adhesive to bond them together. Otherwise, just print and assemble... it's that simple!
Making your own 3D images is easy and fun! Just take a picture from a left eye's perspective, then the right... put them together and print out (they need to be small enough to fit within the focal range). Put inside contraption and re-live those old experiences like you never have before!
I know, I know... your life just got 20 times better... You're Welcome!! :)
Nov 10th, 2015 update: Added the blinder clip for those eyes that can't help but still see two images instead of one, in spite of the aligning lenses. I was surprised at how many people have this problem. Make the card long enough such that it merely blocks one eye from seeing the wrong image. Happy viewing!
November 18th, 2015 update: Here's a card mount that will fit View-Master reels:
And here's a good place to order lenses for about 10 or 15 bucks a pair:
For postcard viewing, I'd use a focal length somewhere in the neighborhood of 75mm(+/-20mm). For Viewmaster viewing, I'd use something with a much shorter focal length like 45mm (same as Google Cardboard lenses). Either single or dual convex lenses will work in both cases.
If you print one out, please let us know what lenses you used and how well it worked out.
Sept 26th, 2016 update: Added a 3D Printed 3D postcard for your amusement. Here's the post: