Re: ATM New mask for Foucault

["Bill T." <twentiethwave@hotmail.com>]

>I'm looking into doing the movement with piezoelectric actuators instead
>of steppers and gears etc, it ought to be a LOT simpler to build but
>still not CHEAP. An inexpensive source of these is:
http://www.micropulsesystems.com/index.html
>
>
>John S.


John,

Those piezo units look pretty interesting.  That's an impressive 
displacement for a piezo actuator.  I wonder what the accuracy is over 
range.

I used a piezo "thunker" on a digital film scanner -- one exposure is taken, 
then a piezo actuator nudges the chip block diagonally one half pixel (just 
a few microns) for another exposure.  Interpolating the two images gives a 
result with (sorta-kinda) double the native chip resolution and much better 
smoothness.  Might be an interesting trick for an astro ccd camera...

The long focal axis throw on my test unit is handy for chasing the caustic 
position around as the focal length changes during repeated figuring steps, 
especially on large and long mirrors or when doing several similar mirrors 
at once.

Computer screens are a good way to go both for their superior geometry and 
for their tamer gammas, as compared to TV's.  Best way is to directly 
examine the image file with software as demonstrated by Michael Peck and 
others.

Bill Tondreau


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