My Adventures with Foucault Testing


To evaluate the figure of the mirror I'm grinding, I decided to build a little tester. I took the basic design from Texereau and built a cheap and dirty version. Actually, I built 2 1/2 of them:


To do quantitative measurements one also needs a Couder screen or something similar.


The hard part of all this is interpreting the results. Here are a bunch of Foucault shadowgrams of my mirror at various stages.

Other mirror testing WWW pages

Foucault tests:

Ronchi & Caustic tests:

Bill Arnett; last updated: 1999 Mar 10