I apologize for my reference to a link that I thought would be free to everyone!
There was no cost for my download of the article, but I guess that's because of Mercer University's 'favored status' (that may
have cost our library a bundle!).
    Let me tell you the basic setup that I have used (similar to Jones').
First of all, Chris--the 'gratings' or Ronchi rulings-are described by Jones as 'grids' having 5 to 70 lines per cm (higher no.
giving better resolution).. It is very easy to generate ones with 5 lines per cm by means of Microsoft paint (by copying and
pasting ever-increasing-sized pieces to form an array) and then from the printed on white paper copy, a transparency (plastic)
using the 'xerox' machine.
    What I built is a small metal box with a partition to separate between the incandescent light bulb on one side and a
'straight through hole' on the other side, behind which one places their eye for viewing.  In front of both sides is the
'ruling' that I made in the manner indicated above.  With this box placed at the center of curvature of a long focal length
mirror--light leaves the bulb aperture, goes through the ruling on that side, out to the mirror, where it is reflected back
through the ruling behind which observation is made.
    When positioned right at the center of curvature, the 'image of the grid' looks like a uniform dark or light field; i.e.,
spacing between lines very widely separated.  As an example of sensitivity, one can place a hand midway between bulb and mirror
and see wave front distortions associated with convective flow (spatial index variations) that results from the heat of the
hand.
     Some students here are getting ready this afternoon as part of the optics course lab I teach to do an experiment with this
setup.  I will try and put some detailed results with setup diagram on my webpage before too long,
    Randall