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Numerical Analysis of Interference Patterns (view source)
Revision as of 07:41, 17 October 2007
, 07:41, 17 October 2007→Phase Shifting Technique
In recent years combinations of spatial and temporal methods have been combined and thus form a subcategory of the phase-shifting method, known as "self calibrating [sic] spatio-temporal algroithms." Among these methods are the Fourier Method, the Lissajou ellipse fitting method, the interferogram correlation method and others. Each of these have their high points and low points, mostly stemming from either the type of surface they best work for or the the number of frames required.
In recent years combinations of spatial and temporal methods have been combined and thus form a subcategory of the phase-shifting method, known as "self calibrating [sic] spatio-temporal algroithms." Among these methods are the Fourier Method, the Lissajou ellipse fitting method, the interferogram correlation method and others. Each of these have their high points and low points, mostly stemming from either the type of surface they best work for or the the number of frames required.
In his paper, Larkin proposes a method mentioned in the previous paragraph that utilizes a "truly isotropic 2-D Hilbert-Fourier demodulation algorithm" or "vortex algorithm" as a solution to the problem of overcoming discontinuities in un-processed fringe patterns. Larkin's algorithm initially eliminates the presence of the offset term a(x,Y) in the general fringe-pattern equation and follows by introducing a weighting function that depends on the frequency of the fringe oscillation. Thus, higher frequency modulations are weighted closer to zero, while those that are closer to DC recieve a higher weight. This tactic, when combined with the vortex transform gives one the necessary
* requires three phase shifted fringe patterns
* requires three phase shifted fringe patterns