[ATM] ATM: FringeXP comparison to professional software

[vladimir.galogaza at zg.tel.hr (Vladimir Galogaza)]

Ric,

>Vladimir,
>Can you expand on what/how phase shift testing
>works,and what makes it more accurate?
>Ric

Not really, but.

Michael Peck mentioned that Malacara has something about this in his
book on optical testing. So I can only quote from Malacara book, chapter 14
"Phase Shifting Interferometry" (written by Greivenkamp & Bruning):

"The single biggest change in all types of instrumentation over the past 20
years or so has been the integration of computers into a measurements
system. Interferometry is no exception, and the primary manifestation of
this situation  has been the development of phase shifting interferometry
(PSI).
Unlike many of techniques discussed elsewhere in this book, PSI is not a
specific optical hardware configuration but rather a data collection and
analysis method that can be applied to a great variety
of testing situations.
While the analysis of static interferograms has benefit from
computerization, it suffers from the need to find fringe centers and the
resulting trade-off between the precision and the number of data points.
Data is collected only along the fringe centers, and most analysis need the
data on a regular greed, therefore requiring interpolation. With a static
interferogram an additional  piece of information is also required to
determine the polarity of the wavefront.

PSI electronically records a series of interferograms while the reference
phase of interferometer is changed. The wavefront phase is encoded into a
variation of the intensity pattern of the recorded interferograms and a
simple point to point calculation recovers the phase. The need to locate the
fringe centers is eliminated as are the associated problems."

Regards
Vladimir.

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