[ATM] No fringes

[Vladimir Galogaza]

>I doubt a green LED is monochromatic enough.  I have
>looked at them with a spectrograph and they have a
>very broad spectrum.  I think I even remember some
>red.

LED spectra are about 30 nm at half intensity points,
similar for green, red and blue.

I do not think that monochromaticism of LEDs is a problem.
It is its size. Usually Newton ring interferometers are shown with
broad (large surface) light  sources (like fluorescent lamps behind 
diffuser).

Regards
Vladimir.