Back in the very 1960's (1961-62 from memory) being unable to source a Ronchi screen (and of course before all the modern tech [printers and such]) i built my own Ronchi screen using 2 x 100 threads per inch brass rods and the fine copper windings from an electrical coil salvaged from an old radio, phone or such. Took awhile to do "the wrap around" of about 2" or a thereabouts, but the end result was worth the effort. Was wide enough to receive return beam through the screen back to the eye. Cant remember what I used as a light source.
Stephen.
