
Windowed Fourier Transforms ◾ 51
and satisfactory for the whole fringe signal. erefore, errors would be
introduced to the phase demodulation by the FT method, as described in
Section 2.2.
2.5.2 Numerical Analysis by WFT with an Invariable Window Size
For comparison, the WFT method is employed for analysis with dier-
ent scale factors. Figure2.16 shows the unwrapped demodulated phase
with WFT employing the scale factors a = 30 and a = 8. Figure2.17 shows
the respective errors. When employing an inappropriate scale factor with
0
100 200 300 400
−10
−5
0
5
10
True phase
By narrow filter
By large filter
FIGURE 2.13 e unwr ...