2D Fourier transform of the dispersed fringes. Spatial frequency is horizontal, whereas the vertical direction encodes the optical path differences seen in the dispersed fringes. From left to right, we see the fringes between B5B6-B2B3-B1B2-B3B4-B1B3-B2B4-B4B5-B4B6-B1B4-B3B5-B3B6-B2B5-B2B6-B1B5-B1B6, with B1=E1, B2=W2, B3=W1, B4=S2, B5=S1, and B6=E2. The fringe contrast is a combination of the visibility of the star and of the instrumental visibility (different from one pair to another).
