Looking at a 3D anaglyph (for red/ green glasses) is an easy way to quickly see 3D in a stereo pic.
But red/ green glasses are not always around and in an anaglyph the color information is lost. A stereo pair can be printed in color and then viewed in a 3D viewer, but who wants to print everything.
Another option is the cross eye method, but if you want to show family and friends, hardly anyone can see and many complain about headache... (???)

This viewer is easily adjustable in height and distance to the screen.

Materials: 2 wooden boxes
a (piece of) mirror
discarded halogen fixture

tools: saw with fine teeth or hacksaw and small files for finishing
glass cutter
glue

Step 1: The Base

Halogen fixtures ('study light') have been around for a while, so it is easy to pick one up a discarded one.

Remove the power cord and the top part where the lamp should be. Replace it by a piece of wood which can tilt back an forth, not too easy. Later the viewer will be glued on this piece of wood.

The 12 V transformer in the base is nice and heavy so the viewer will not topple over very easily. The fixture can tilt back and forward, the height can be adjusted

Step 2: The Inside of the Viewer

The viewer itself is made from a wooden box. The side toward the computer is mostly open. At both ends there is a mirror at 45 degrees, reflecting the light from the screen inside the box. In the middle of the box are 2 mirrors in a V shape of 2 X 45 degrees reflecting the light out of the box toward the observer. 2 holes on this side allow the light to reach the eyes.

Step 3: Building It

Cut the glass. the outer pieces should be as large as possible. I made them stick out of the box. Instead of making them rectangular, a trapezium shape would be better (wide ends on the outside). Next time better.

Cut one of the boxes diagonally. make a hole or slit at the bottom in the middle (see picture). This will serve as the mirror holder for the central part, towards the eyes. The lid of this box is not needed.

The screen side of the other box, which should be quite elongated, has to be cut in order to allow the view on screen to enter the box. Best is to take the mirrors, hold them in the proper position, and draw the line where to cut. The lid has to be cut in a similar way. The holes for the eyes have to be made as well

To support the outer mirrors, 2 pieces of wood have to be glued inside the box at 45 degrees (eye side). The mirrors can be glued on the wood with silicone putty.

I fixed the outer mirrors in the box, the inner mirror holder is bolted on the lid. Some play back and forth might be handy.

The picture shows the lid upside down behind the body.
In order to clean the mirrors I did not glue the lid on the body

Step 4: Displaying and Viewing

A simple way to prepare the images for viewing is to stick them into Word. The size is dependent on the dimensions of the viewer, always the same. So if you insert the pics in the document at full page width, check out which zoom factor is appropriate. Next time use the same factor, and display is always OK. Of course always check what is left and right, a good idea is to always name the pairs picL and picR.

Another cool experiment is to look through the viewer to objects in the room. Depth is greatly exaggerated, plants look very cool. This phenomenon is called hyperstereo