I once read a "career lessons learned" essay from a retiring engineer at JPL's Division 35. On mechanisms design he said "Never design to fit an already existing size envelope. Design the mechanism first." I agree, but often it happens the other way around.

      Before I got involved, this project was designed to a customer's optical component layout. The lenses were held in place in the colored holders, and could shift +/- 3 mm side to side. The design was done and the size of the holders was established.

      The holders were only about 4 1/2 inches tall, and I had to add the ability to focus the lenses +/- 6mm along their axes. I had to retain the side to side shift and was not allowed to spin the lenses. In use, only the tops of the lens holders were accessible so both adjustments had to be made by hand from the top.

      What you see here is the result. I put synchronous jack screws into the 4 corners that were operated via timing belt with a knob. The whole effort, including a full set of drawings, took 2 weeks.