ATM making a multi-capable tester

["Bill Morgan" <sass5@erols.com>]

Hello everyone,

 

I'm finishing my foucault tester and have some questions. I want to make it with the flexibility of being able to do each of the following:  the poor man's caustic, pin hole, wire, slitless and ronchi tests. I'm having difficult understanding the mechanics of some of them. Please be patient with me, I've read through the archives and the books (Tex, and ATM I) and am a bit puzzled.

 

a. Poor man's caustic. The blade is fixed to the tester (either at one end or in the center) but is able to rotate or rock. ATM I, states that for the caustic tester use screw, which is attached to the blade as a mechanical means of moving the blade. Is this required or can it be moved manually. Also, is a dial gage required?

 

b. Pin hole. The pin hole from what I understand is used for several of the above mentioned tests. What is the recommended hole diameter(s) for testing fast mirrors; say, f/6 or 5? In ATM I, the added note on section B.16.5, page 334 gives a formula limiting the as:  0.0026F/D [mm].  Is this a valid formula to be used ?

 

c. Wire test. Does the wire go in front of the pin hole only or does it need to extend to a point where it can be viewed with the eye; as it does with the slitless tester?

 

d. There are different methods for doing a ronchi test, depending on the type foucault tester used,i.e.,either a fixed or moving light source, which determines how the grating is used. My tester is the moving light source type and from what I gather, the ronchi screen covers the the light source in part and extends to where the eye can view through part of the grating as well. Am I correct here? I have the Edmonds 100 line grating for this test.

 

e. I'm using a defused 12000 mcd orange LED as the light source, is this ok for all the above tests, or should I have a brighter light source for the wire and ronchi?

 

f. I need a clear description of the pin stick and how to use it when making tests.

 

I may be way off track with my questions (and I'll probably more), but when I started reading material on the different testing methods my head started swimming. I only knew of the foucault in its simplest form, now I've learned there are hi-bred versions as well. So, instead of making one type of tester, I decided to make them all in one.

 

 

Many thanks,

 

Bill