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Digital speckle-pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle
A Andersson1, A Runnemalm, M Sjödahl
1Division of Experimental Mechanics, Luleå University of Technology, SE-971 87 Luleå, Sweden. angelica.andersson@mt.luth.se
Applied Optics
|March 8, 2008
Summary
Digital speckle photography (DSP) compensates for large in-plane motions in digital speckle-pattern interferometry (DSPI). This technique improves fringe contrast and enables absolute phase unwrapping for accurate deformation analysis.
Area of Science:
- Optical Metrology
- Experimental Mechanics
Background:
- Digital speckle-pattern interferometry (DSPI) is sensitive to environmental vibrations and rigid body motions.
- Large in-plane motions can degrade fringe contrast and hinder accurate phase analysis in DSPI.
Purpose of the Study:
- To demonstrate the compensation of large in-plane motions in DSPI using digital speckle photography (DSP).
- To improve fringe contrast and enable absolute phase unwrapping in DSPI measurements.
Main Methods:
- DSPI recordings are recombined and analyzed using DSP.
- DSP results are utilized to compensate for bulk speckle motion before phase map calculation.
- DSP results serve as an initial guess for absolute phase unwrapping.
Main Results:
- High fringe contrast is achieved even for deformations spanning several speckle diameters.
- Absolute phase change can be unwrapped for in-plane deformations using the DSP initial guess.
- The method's principles are validated through experiments involving in-plane rotation and plate encounters.
Conclusions:
- DSP effectively compensates for large in-plane motions in DSPI.
- The combined DSPI-DSP approach enhances measurement accuracy and robustness.
- This method offers a significant advancement for deformation analysis in experimental mechanics.
