Monday, November 27, 2017

Mirror Cell

Traditional mirror cells hold the mirror in place with clips that are flat metal with a 90 degree bend. One part is held to the outside of the cell where the hole for the screw can be far from the edge of the clip.  Attaching on the front face of the cell gives limited room for the screw hole.  I think I have been successful, even though the hole is. 151" diameter,  .090" from the edge of the clip.  I still need to assemble and make sure that it all works.  My clips are a bit longer than I want (blocking light and adding reflections, even once painted flat black) so I will mill them to length tomorrow.  My wife thinks working to hard on these things is part of my voice issues when I lecture,  and I think she is right.  Monday is so nothing day.

The mirror cell is about .37" too deep,  so I can either pad the bottom with double sided foam tape or turn the outer tube by that much.  I am getting tired of the work involved;  so I think I will go with the foam tape.

1 comment:

Will said...

One of the ways I've mounted high quality imaging mirrors was in an aluminum ring. This was done with spots of rubber type (usually) epoxies, injected through holes radially located. Set it on a table, use a number of shims to locate the optic in the center, and start injecting dots at/near opposing sides, until you have the optic fairly well located, then go back and add more until you get the diameter spot you want. Avoid air bubbles. This mounting style was termed "Potting".
You still want to be careful not to stress the shell/ring when you mount it, as you can distort the element, depending on weight/size and image quality needed.

The only optics I used clips on were CO2 laser mirrors, and these clips were on the back. The working surface sat on three dowel sides that were machined to create a co-planar surface. They projected out of the side of an aluminum cell that was tilt adjustable. They had to sit on the mirror coated side to allow replacement mirrors to just be dropped in without losing laser beam alignment (burning a mirror was a somewhat common occurrence). After initial factory alignment, the cell was basically frozen in place by doing a variation of that potting method. VERY robust result! The laser arm assembly (7 joints, 2ft folded) could be tossed on the floor without losing beam alignment. The prior design would drift out of alignment when the system was rolled over doorway thresholds in the hospital.
That surgical laser company is gone, and so is the one that bought it for that arm. Redesigning that laser system was a neat challenge. Typical Silicon Valley product, they put an R&D design directly into production.