Describes various test rigs which are easy and cheap to build.


Copyright P. J. Smith

But permission is given to distribute this material in unaltered form as long as it is not sold for profit.



A range of possible Ronchi test rigs is presented. A huge number of approaches are possible and anyone with a minimum of supplies can successfully implement this test.


Beginners are best served by initially constructing one of the simple types. I suggest either the Starter Kit Rig or Basic Rig with the Deluxe option added later.


Since measured movements of the Ronchi grating is unnecessary for normal Ronchi testing, none of the following include this feature. [1] Of course, you can use a precisely controlled Zonal Foucault Tester with calibrated slide for Ronchi testing if one is available.




Starter Rig is suggested as a quick way to begin if you are using a professional grating.


Basic Rig works well. It is quick to make and versatile.


Deluxe Rig is simply the Basic rig with fine tilt adjustment of the slit. It is versatile and highly recommended.


The Brute is a high wattage rig for multiple surfaces working extremely close to the axis. Crude but effective.


Simple Rig is mobile and uses a flashlight and aluminium extrusion. Best for rough testing.


Emergency Rig improvised from a small flashlight.


Laser Diode Rig uses the point source of a Laser Diode. Easy to set up but not normally recommended.


Crude Mirror Stand with simple tilt adjustment is a necessity. Avoids broken mirrors !



[1] Some people combine measured longitudinal grating displacement with Ronchi testing when attempting to estimate the degree of asphericity. This is of course unnecessary when testing Spheres. See under Aspherizing for more details.