ATM (Fwd) BOUNCE atm@shore.net: Non-member submission from [kevin@

["Mel Bartels" <mbartels@efn.org>]

------- Forwarded Message Follows -------
Date:          Fri, 16 Aug 1996 16:59:42 -0400 (EDT)
Subject:       BOUNCE atm@shore.net: Non-member submission from [kevin@aquilagroup.com 
(Kevin Ferguson)]

Subject: ATM Bath inteferometer

 
Tried to e-mail ric rokosz directly, but bounced...perhaps he has new
address, Perhaps someone else can help, so I ask publicly:

A while back Ric Rokosz posted a quiry about this inteferometer to the ATM list.

I am now trying to get one of these to work also.  I had pretty poor luck
with the clay mounting routine, but have started building up the all-thread
and wood plate version that followed (author??) K.L. Bath's article in ATMT I.  

I am using a HeNe laser as a source, and so far it doesn't seem too
difficult to align.  The bright spots really help, though the spurious
reflections from beamsplitter cube are killer bright...I worry about
damageing my eyesight...final version will need stops to catch these for sure.
I still have to make mounting plates for a couple more elemnts, but so far
have laser, spatial filter (?? see below) and main beamsplitter mounted and
aligned.

BTW, I am using porros from 10x50 binoculars, luted with corn oil from the
kitchen...seems to work OK. I squeezed them as tight as my fingers would
allow for 2-3 minutes, then wiped off excess oil with acitone.  I see no
sign of oil oozing out in several evenings of experimentation.

>From what I gather in the archives, spatial filtering of the laser is a good
idea, at least with other interferometer designs..  Not sure what this is
exactly, but I have tried illuminating a pinhole with laser, and then
collomating this using short focal length (~5mm) lens from minature video
camera.If I defocus a bit, I project image of pinhole, showing irregular
edge, and distinct diffraction effects.  Also, I see concentric interference
bands which I assume are coming from internal reflections in the lens.  This
allows simple centering of the lens, but will it hurt proper function of the
interferometer?  I seem to have plenty of light without an upstream lens to
concentrate light on pinhole..assuming I have enogh light, I figure this is
one less complication in already involved instrument?

At any rate, decreasing the source brightness seems advisable while
experimenting...I still have plenty to put spots on optical surfaces, and
more just increases danger of putting damaging beam into my eye. Maybe I'll
add a concentrating lens if I later find need for more light.

Ric was advised to give up, and impliment a Ceravalo design.  I am hoping
he, or someone else, ignored that advice, and can now help another to get
this beast working.
Do I hope in vain?

-KF-