Strain measurement by heterodyne holographic interferometry

Area of Science:

• Optics and Photonics
• Materials Science and Engineering
• Mechanical Engineering

Background:

• Interference phase measurement is crucial for analyzing material deformation.
• Holographic interferometry offers non-contact, high-resolution measurement capabilities.
• Heterodyning enhances phase measurement accuracy in interferometric techniques.

Purpose of the Study:

• To review the fundamentals, possibilities, and limitations of heterodyne holographic interferometry.
• To report experimental results of strain measurement on curved surfaces.
• To compare heterodyne holographic interferometry with quasiheterodyne methods.

Main Methods:

• Utilizing heterodyning in double-exposure holography for automated interference phase measurement.
• Employing three double-exposure hologram recordings with varying illuminations to determine vector displacement.
• Calculating local derivatives of the displacement field to derive strain components.

Main Results:

• Achieved a sensitivity of 1 microm/m for strain components.
• Demonstrated a spatial resolution of a few millimeters for strain analysis.
• Successfully performed quantitative evaluation of 3-D displacement and strain on a curved object surface.

Conclusions:

• Heterodyne holographic interferometry enables high-resolution, automated, and quantitative 3-D displacement and strain analysis.
• The method provides high sensitivity and spatial resolution suitable for detailed material deformation studies.
• Comparison with quasiheterodyne techniques highlights the specific advantages of the heterodyne approach.