Dynamic electronic speckle pattern interferometry (DESPI) phase analyses with temporal Hilbert transform

Area of Science:

• Optical Metrology
• Experimental Mechanics
• Signal Processing

Background:

• Dynamic Electronic Speckle Pattern Interferometry (ESPI) is crucial for measuring small deformations.
• Traditional phase analysis methods can be sensitive to noise and intensity fluctuations.
• Accurate temporal analysis of deformation fields is essential for understanding material behavior under dynamic loading.

Purpose of the Study:

• To develop and validate a novel Hilbert transform (HT) based method for phase analysis in Dynamic ESPI.
• To process interference signals in the temporal domain for precise deformation field mapping.
• To enhance defect distinction and sign change determination in deformation measurements.

Main Methods:

• The Hilbert transform (HT) was applied to the temporal history of interference signals at each pixel.
• Bias intensity fluctuations were removed before applying the HT to improve phase calculation accuracy.
• The method was tested in two distinct experimental setups to evaluate its performance.

Main Results:

• The method successfully generated a temporal development of the two-dimensional deformation field.
• Defects were clearly distinguished, and the sign of deformation was accurately determined.
• The measurement range spans from submicrons to tens of microns.
• Improved spatial resolution was achieved compared to fringe analysis and spatial carrier methods.

Conclusions:

• The proposed Hilbert transform (HT) method provides a robust approach for phase analysis in Dynamic ESPI.
• This technique offers enhanced accuracy and spatial resolution for measuring dynamic deformation fields.
• The method is effective for identifying defects and determining deformation sign changes in various experimental scenarios.