Complex amplitude correlation for compensation of large in-plane motion in digital speckle pattern interferometry
Angelica Svanbro1, Mikael Sjödahl
1Division of Experimental Mechanics, Luleå University of Technology, Luleå, Sweden. Angelica.Svanbro@ltu.se
Applied Optics
|November 23, 2006
Summary
Complex amplitude correlation offers direct deformation retrieval in digital speckle pattern interferometry, unlike digital speckle photography. However, its effectiveness diminishes with significant phase gradients in subimages.
Area of Science:
- Optical Metrology
- Experimental Mechanics
- Image Processing
Background:
- Digital speckle pattern interferometry (DSPI) is sensitive to in-plane motion, complicating deformation analysis.
- Existing methods often require complex post-processing to compensate for motion artifacts.
- Digital speckle photography (DSP) uses intensity correlation, which has limitations in direct phase retrieval.
Purpose of the Study:
- To investigate complex amplitude correlation for compensating large in-plane motion in DSPI.
- To compare the performance of complex amplitude correlation with intensity correlation used in DSP.
- To identify advantages and limitations of complex amplitude correlation for deformation measurement.
Main Methods:
- Complex amplitude correlation was applied to digital speckle interferometry data.
- Experimental results were compared against those obtained using digital speckle photography.
- Correlation values and wrapped phase maps were analyzed for both techniques.
Main Results:
- Complex amplitude correlation directly retrieves the phase change related to deformation from the correlation peak.
- This eliminates the need for separate motion compensation and interferometric algorithms.
- A drawback was observed: correlation values decrease rapidly when subimages contain phase gradients exceeding pi.
Conclusions:
- Complex amplitude correlation is a promising technique for motion compensation in DSPI, simplifying deformation analysis.
- Careful selection of subimage size or incorporation of a phase variation compensation parameter is crucial for its effective application.
- The study highlights the trade-offs between direct phase retrieval and robustness against phase gradients in correlation-based methods.
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