Re: [CAD_CAM_EDM_DRO] autocollimators (was Test Peice for 3D finishing)

> > Now if you turn the mirror even a tiny amount, the return beam moves.
> >
> > The process is incredibly sensitive. As part of my physics education we
> > had a class where we had to measure a number of different things, all to
> > various insane accuracies. One of the things we ended up with was the
> > speed of light.
> > Our set up consisted of a laser fired down a hallway. 80' or so away
> > was a mirror at a slight angle. The return beam hit a second mirror
> > parallel to the first, and so "walked" back and forth 4 times, then off
> > into a telescope.
> > The thing was insanely sensitive to vibration. We had to do the experiment
> > at 3am on a weekend to get the building "quiet" enough to not vibrate.
> > Then we had to sit quietly for a long time before we could take measurements.
> > The beam went crazy once when a truck drove by outside.
> >

Perkin Elmer had to remove the speed bumps from their parking lot when
they were making the hubble telescope mirror.

Unfortunately, someone shimmed the primary measurement jig with a few
random washers when it didn't fit together the way it was supposed to.

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
(617) 629-9830 home (temporary), 253-2606 MIT