How you can use a Nintendo 3DS to make and view stereoscopic 3-D images without glasses.
Tag: Stereoscope
How to View Stereoscopic 3-D Images: Free-Viewing and Using Stereoscopes
There are different ways to view images in a stereopair and they all rely on each image being viewed separately by the corresponding eye so your brain can fuse the two 2-D images into one 3-D image.
What is Stereoscopy?
Well, it'd be a bit naughty to start a blog about stereoscopy and not say what it is! In a nutshell: Stereoscopy uses the illusion of depth to create a single 3-D image from two flat images when viewed by each eye separately.
The Stereoscopy Blog 