Application and Optimisation of the Spatial Phase Shifting ...

3.2 Phase-shifting ESPI 71
ν x 0 is that S
~ ( ν ) and C
~ ( ν ) point in almost opposite directions, while they have nearly the same
x
x
argument at ν x ν N . As mentioned above, for ν x =0 and ν x =ν N , no phase information at all can be retrieved.
The correct value of bsc(ν x ) appears at ν x =ν 0x for α=90° or 120°, respectively. It is interesting to note that
the p-v phase errors increase symmetrically for ν x ≠ν 0x when α=90º, while for α=120°, they rise more
steeply for ν x >ν 0x than for ν x