a)
b)
c)
d)
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!)