Re: [ATM] testing an f/2.6 mirror?

[Dominic-Luc Webb <dlwebb@canit.se>]

On Wed, 19 Dec 2007, Vladimir Galogaza wrote:

> >by the odd  few microns, while turning the dial. With a remote,
> >computer controlled stepping-motor setup however, this has
> >not been a problem for me,  even  with a set-up that is far
> > from rock-steady.

> With minimum five adjustments to touch and turn it is disastrous.
> When I touch dials everything changes and I have to turn dial, leave it
> and wait until everything sets, to see effect of turning.

I have used floppy drives for such jobs by just mounting testers, etc
straight onto the read/write head, and sending step instructions
through the parallel port. These have been kind of clunky actually,
amd they give some vibration. Note that the steppers used in early
drives got replaced by actuators, etc.

My latest mechanical tester looks like it will end up being the
winner in terms of stability, more on that when it is complete.
Looking around my lab, thinking on my years of using various
motion control manipulators, the smoothest ones, which are my
favorite, are hydraulic. The ones in my lab give very smooth
vibration free sub-micron motion. There is a small, heavy box
with a piston driven by a fine threaded screw, and this pushes
or pulls fluid through a thin cable that extends to where the
work needs to happen. Having this box isolates the user from the
object to be moved. I think on the other end there is just another
piston and the object to be moved is connected directly to that.
It is mechanically primitive, and works great.

Dominic

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