The Cheap and Dirty Foucault Tester

Mark III

Derived from the highly successful Mark II, the Mark III is much more capable thanks to the addition of measuring scales (for use with a a Couder screen) and various other minor improvements.

Here's the back side (the side toward the mirror):

Here's the front side (the side you sit behind):

Here's the auxilliary laser pointer alignment tool. This makes aligning the mirror a snap.

And finally, the scales. I hacked them up with Photoshop, printed them out and stuck them to the tester. Each rotation of the screw moves the carriage 1/20 of an inch which corresponds to one division of the linear scale in the back. The scale on the knob is divided into 50 increments each of which is just 1/1000 inch. With a little practice I've been able to get repeatable measurements to about .005 in.

Further Improvements

Remaining Problems

See the Mark II page for more details.

In Action

Here are some images of Foucault shadowgrams taken with my Mavica digital camera.
Bill Arnett; last updated: 1999 Mar 10