Make a 3-D Stereoscope Slide and Video Shooter

Step 7 About the Convergence System

When doing my initial tests, I simply left the screws on the large mirror mounts slightly loose and manually set the two sides so the left and right images appeared to be similarly composed. I could compare the positions of the two mirrors to the base plate to keep them more-or less equal, and found that this was accurate enough. But the process was clumsy and I eventually added a more convenient system to quickly adjust the two large mirrors for convergence. This is the most complicated part of what otherwise is a very simple project, actually.

There are probably many ways this convergence control could be designed, but I used a small cam on a shaft that pushes a 1/4" aluminum rod rearward. At the end of the rod there is a piece of plastic that pushes on a pair of aluminum rods -- one that is attached to each of the large mirror mounts. Holes for these rods are also best made prior to gluing the mirrors onto the mounts, and with my system there are also small holes for pins that hook onto the return springs. The return springs attach to the outside ends of the large mirror mounts to pull against the cam, push-rod, and mirror rods. I also used little push springs on the large mirror mounting screws to allow them to move quite freely but stay flat against the base plate.