ATM Revolutionary Optical Test

[astillma@nit.AirTouch.COM (Anthony Stillman)]

This news just in, a revolutionary optical test based around a simple knife 
edge test jig has been developed.  This straight forward test is capable of 
simultaniously sampling numerious regions of a mirror.  It is capable of 
detecting slope errors less than 2 milliradians.  And best of all you don't 
need any expensive lasers which produce dangerious ionizing radiation in most 
bad 60's si-fi movies and some good ones.

What is this amazing and radical test that could possibly bring an end to the 
hundards of hours spent squinting at foucult shadows?  What recolutionary idea
could possibly measure directionaly invarient surface slopes to high accuracy 
with common house hold items?  Well before I tell you that, let me tell you 
about the benifites of owning your very own condo here at Kumoni Kidu!  Oops, 
sorry, wrong sales pitch.  Let me tell you the simple items you will need.

You will need a knife edge jig which you can modify and has an extended range. 
You will need a single lens reflex camera with a removable lens.
You will need an opaque material at least the size of your mirror.
You will need an Exacto knife.
You will need to know the radius of curvature of your mirror.

Sounds do-able, doesn't it?  Here's how easy it is.  Remove the camera lens 
from the camera body and put it aside in a safe place, you won't need it for 
the test.  Remove the knife edge from the knife edge jig and mount the camera 
body in its place.  Cut any number 1" to 3" holes (depending on the size of 
your mirror) in the opaque sheet.  These holes should be at increasing distances
from the center of what will become your mask and those distances should be 
measured carefully and recorded to use in reduction.  Be resonable with how many
holes you cut.  Assemble the test apperatus as you would a foucult test 
and place your mask directly in front of the mirror on its test stand.  In 
a compleatly dark room turn on your pin hole light source and adjust the jig so
that the camera's film plane is approximately at the radius of curvature.  Now
move the camera back from the radius of curvature a few inches and take a
picture.  A camera reliese cable can help here, as the exposure may need to be 
long, given how dim pins hole tend to be.  Next while measuring carefully the 
distance traveled, move the camera froward a few inches in front of the radius 
of curvature and take another picture.  Have the film developed.  Thats it, 
thats all there is, except of course the reduction.  Which I'll explain if 
asked.

Oh, and what is this miraculous test called.  The Hartman test.  And now you 
know the rest of the story.



Anthony