The Holo-Diagram. IV: A Practical Device for Simulating Fringe Patterns in Hologram Interferometry.

A new simple moiré equivalence to hologram interferometry has been investigated. We have found this equivalence to be very useful as an educational tool. The analogy to any interference pattern can be projected before a large auditorium using an ordinary overhead projector, and the fringes can be studied directly during formation. The equivalence is rather easily understood as it is only based on the loci of constant pathlength for the light traveling from the light source to the observer via the object. No, or very little, mathematical, optical, or linguistic preknowledge is needed, because the ellipsoids onto which the method is based can be demonstrated using just two nails and a string. The new equivalence method is also being tested in a simple analog computer, which, we hope, will be used as the holographer's sliderule.