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Re: ATM Bath interferometer

It is apparant that I have commited one of my pet peeves, namely citing a
reference (ATMT I) which few apparantly have aceess to.  I have recieved a
couple of offers of help, but it is apparant that the configuration of Herr
Bath's interferometer design is not widely known.

Omitting my attempts at spatially filtering the laser beam, here is my best
ASCII art shot at showing how this works.

<html><pre>
          eye
           *                     sphere under test
   50% mirror                           \
                     ^                   \
HeNebeam \         /   \      DCX         |
 ---->----\-------/_____\--->--|--->      |
          /       \     /--------->       |
         /         \   /                 /
        /            V                  /
   100%mirror   beam splitter/combiner
</pre></html>

 
hopefully I put spaces insead of right arrows in there.  Basically  the beam
splitter cube is used as two dove prisms, with the normal total internal
reflection of the upper prism being degraded by oil luting, to partial
transmission, allowing the beam to enter the lower prism, forming the lower
exiting beam. The upper beam transits a dove prism, while the lower beam
passes through a plano-plano plate.

The lower beam bounces off the center of sphere under test, and returns
through the DCX lens.  The upper beam follows a congigate path. going first
through DCX lens, then reflecting off mirror under test, then returning to
lower half of cube.

>From the two articles in ATMT, it is not apparant if an eyepiece is required
at the eyepoint shown.  There is a second exit available, via the 100%
mirror (I haven't put this mirror in yet), and Mr. Bath's drwing shows a
lens forming an image on film here. I took this to mean that the light was
approximatly colimated, and needed to be brought to a focus, thus have been
trying without an eyepiece to see the "disks" Mr Bath refers to.  I showed
the 100% mirror to make the location of second exit apparant, but I have
omitted it from my device.

 Mr. Bath shows a white light source, with stops, and colimating lenses, but
says "best is a laser"  He states that the stops and collomating lenses are
not required with a laser, but, alas, no drawings of this.

Mr. Bath showed a second beamsplitter cube at the location where I have
shown 50% mirror.  I had the mirror, and there are enough stray reflections
from main cube without adding more surfaces! Bath stated that a microscope
slide was a good substitue, so I figure a half aluminized diagonal aught to
be OK.

One of the locals asked why I am doing this, and I don't really have a good
answer.  A defunct pair of 10X50s, and a barcode scanner with a HeNe laser
were given to me.  So far I have spent . $5 on this project, so the scot has
to ask "why not?".  The cash outlay is certainly acceptable, and my time is
being repaid with a lot of knowlege and experience. 


-KF-