RONCHI  RIGS

Basic

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Copyright – P. J. Smith

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


 

BASIC TEST RIG

 

This test rig is similar to a simple Knife Edge tester.

 

The main difference is a holder for the Ronchi Grating, which is simply a commonly available 35 mm slide mount held with a bulldog clip.  This is versatile, protects the grating, and is convenient if you wish to experiment and make many quick changes.

 

 

By omitting the Slide mount the grating may be mounted a little closer to the optical axis, but if this is important look at the principle used in the Brute test rig.

 

The light source may be a small light bulb (preferably the type with a built in lens) or a red LED. 

The red LED, which is probably the best, is best unmodified. 

Simply drill a hole and push it in place. 

 

In front of the light source must be a ground surface of glass.  A small piece of thin glass ground on both sides is convenient.  Microscope slide, window, or picture frame glass is excellent. [1]  See diffuser.

 

If you use a slit scribed on black painted glass, the rear surface of the glass may be ground.  This then becomes the diffuser. See scribed slit.

 

One easy way to hold the slit in place for experiments is with blobs of BlueTac or modelling clay.

 

The 35 mm slide mount may be held with a small Bulldog clip from the top.  It is secure and simple.  If this is not too large, it is easy to adjust the tilt of the grating with your fingers.  An extension handle makes it more sensitive but is not absolutely necessary. See the DeLuxe and Starter rig for a better tilt adjustment.

 

The entire unit should stand about 10 inches high and the cut-out on each side should be large enough for your nose.  A cut-out on each side caters for both left and right hand viewers.

 

To use the unit in the Grating/Grating mode, simple remove the slit and slide the grating partially over the light on the front of the frame.  A piece of ground glass must be used between grating and light.  You may need a spacer in front of the frame to keep the slide mount from hitting the source.  Examples are found under the DeLuxe and Starter Rig.

 

For more delicate tilt adjustment (only needed in the Slit/Grating mode), see the Deluxe Tilt rig.

 

If you need to get closer on axis, see the Close in Brute Rig.

 


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[1] See under slits and sources.  Also under Diffuser.