Re[2]: [ATM] On Axis Foucault (try this instead)

[Richard <cnc@cncservo.co.uk>]

Hi David,

Wednesday, June 15, 2005, 3:47:48 PM, you wrote:

DH> I and others (most notably John Sherman) have been preaching this for
DH> decades; and yet we just can't
DH> make it catch on.

Not sure what it is that we can't catch onto David, but maybe
you can draw on your experience to help me please.

I have to test a 2" F/2 spherical mirror (yes, TWO inch).
Actually it has focal length 100mm and usable diameter 50mm.
Ideally I would like to get it to lambda/20 or as near to
perfection as I can over the central 80%, as it will be the
reference element in an interferometer and any error in it will
cause errors in everything that is ever tested with the
interferometer in the future.

Could you talk me through a layout for Focault testing it
please?. Assume ignorance as I haven't done this for many years.
Eg, I don't know what to use for an abberation free light
source. What I do have, that I can pull off my microscope, is an
X-Y table with 1um/0.0001" digital micrometers. Also have a
laser, microscope objectives, smattering of lenses, LED's,
pellicles, cube beamsplitters, digital camera, poor eyesight.

I'm happy to send it away to a calibration lab to assure it's
final quality, but any help in achieving it would be much
appreciated.

-- 

Best regards,
  Richard in the UK



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