Re: Re[2]: [ATM] On Axis Foucault

[aplanatic@aol.com]

 Richard,
 
In the Foucault test the SA from a cube beam splitter is not cancelled by passing through the splitter twice.  Each pass through the beam splitter adds SA in the same direction.  
 
The SA from a cube splitter is very significant for an f/2 system.  Just ray trace to find out.
 
-- Dave
 
-----Original Message-----
From: Richard <cnc@cncservo.co.uk>
To: Vladimir Galogaza <atm@atmlist.net>
Sent: Tue, 14 Jun 2005 19:23:56 +0100
Subject: Re[2]: [ATM] On Axis Foucault


Hi Vladimir,

Tuesday, June 14, 2005, 7:11:43 PM, you wrote:

VG> Is it possible to equate aberration caused by the cube beamsplitter in
VG> interferometer with its use in (on axis) Foucault tester ?

Not sure what you are asking Vlad. Would the SA be the same as
one arm of the interferometer?. If the geometry of the latout
was the same, then yes. Where it differs, if I understand the
original idea, is that the outgoing beam does not take an
identical path to the returning beam.

Thinkning about it a bit more, I think the SA could be nulled.
Consider the light source to the right side of a cube
beamsplitter and the KE behind the cube (inline with the
mirror). The outgoing beam travels through half of the cube,
reflects through 90 and travels through another half of the
cube. The returning beam travels through half of the cube,
transmits across the semi-reflective surface then travels
through the second half of the cube to the KE and then the eye
or camera. Each beam will suffer some degree of SA, albeit
opposite in sign. I would conclude that if the light source
origin to cube distance is equal to the eye/CCD/sensor/camera
plane, then the two beams will suffer equal but opposite SA and
the SA will cancel.

-- 

Best regards,
  Richard in the UK



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