Re: [ATM] The Flexed mirror

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

On Tue, 15 Jan 2008, Russell Jocoy wrote:

>     As Bob May mentioned, and which was brought up on this list years
> ago, was to flex the polished, spherical mirror the opposite way and
> polish a "new sphere" on the surface, then "un-flex"  In theory you
> would have the classic Parob..  Has anyone attempted this??
> I also recall sectional heating in the center while polishing
> "spherically" and then cooling to norm. to imitate the
> "dig"....Are we getting to deep here??    Russ

I can't say anything about "too deep", but these concepts are not
new. Flexing an optical surface for grinding/figuring, etc is often
done for other lenses and mirrors, but the term "FLEX" may not pop
up. This is essentially how Schmidt corrector plates are made,
albeit, the flexing that has been discussed on this list has been
accomplished by hydraulic/vacuum methods. I have a few strategies I
am tinkering with for production of Schmidt correctors. One of them
involves flexing. Another is a record turntable in which the
swing of the arm is timed according to the shape of the curve.

I have gotten side-tracked on this because of a lot of hurdles to
overcome in the primary mirrors in which I am using thin slumped
plate glass. Testing had to be done with the mirror in a proper cell,
and then I discovered that the back surface, as luck would have
it, has an almost common center of curvature with the front surface.
So, the back surface contaminated my optical tests. I now have
images to prove this using marks on both sides, and optical masks
that give double images. Obviously I can grind the back, but
since the two sides are not a perfect match, I somehow drifted
off into thoughts on how to confocalize my optical test equipment.
I reckoned it would be useful in producing thin concentric meniscus
lenses, which I am also interested in. I see FLEX ending up
being used in perhaps a couple stages of Schmidt camera
construction, and I have tinkered with it for many years. So
far I just have not had much to report more than what others
have already reported.

Dominic

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