The light from a CO2 laser
in the lab is split and sent to the two apertures of MIDI. By moving the
internal delay lines by steps of l/4
(about 2.5 µm for the 10.6 µm laser light) we can obtain destructive
and constructive interferences on the two interferometric channels (the
two circles on the top of the image), passing by a state of equal brightness
on both channels. The figures show, from a) to d), this sequence.
The images are obtained from the average of 100 raw frames with 500
µs integration time each.
Later, a movie was obtained with a Blackbody as artificial source and
with a grism. By scanning the OPD, we can see constructive and destructive
intereference only for some wavelengths, until we come to the white light
fringe.
You can see or download the movie through this link
(big file: 4 Mbyte!)