Re: ATM CCD Foucault tester?

["Bob May" <bobmay@nethere.com>]

Remember that the camera is equivalent to an eyeball.  What's nice about the
camera is that you can change it's focal length at will.
I use a security camera at the SDAA mirrormaking group and have excellent
results with it.  I have replaced the original lens for the camera with a 1"
or so ( I think that it's a eye lens from a 10x50 binocs) lens and that is
just about right for most of the stuff that is being done there.  You want
to pretty much fill the view with the mirror (you can cut off a bit at the
top and bottom on the Foucault test with no problems) with whatever lenses
that you decide to use.  You do want to get the lens as close to the knife
edge as possible (you do that with your eye also) so that you see the light
from the mirror as best possible.
When you do setup a camera, I suggest that you apply a second LED off from
the knife edge so that the returning beam can be used as a prepositioning
locator of where the light is going to be for the knife edge light.  We have
a large superbright LED and a target on the other side which allows me to
locate the position and general focus of the mirror and be running the
Foucault test in about 1 minute from the time that I start adjusting the
pointing of the mirror (a jackshafted lifter on the mirror mount makes
locating the mirror's return real easy as you can just sit there at the
tester end and move the mirror about as desired!).  One guy in the SDAA
group loves to see how long it takes from the moment that I walk up to the
tester and get a center zone reading on a mirror that gets put onto the
monitor's screen.  He's measured about 20 seconds on one case and is still
looking for something shorter.  Same mirror testing isn't included in his
timings.  What I'm saying is that the setup with the targeting LED makes
things go extremely fast!
Bob May
My new web space address is http://webu.wigloo.com/bobmay/ or
http://nav.to/bobmay
and my new email address is bobmay@nethere.com
Bob May