Slope measurement of bent plates using double grating shearing interferometry

Area of Science:

• Optical Metrology
• Interferometry
• Mechanical Engineering

Background:

• Accurate slope measurement of deformed structures is crucial in mechanical engineering and material science.
• Traditional grating-based techniques often require complex optical setups, including spatial filtering, limiting their practicality.
• There is a need for compact and efficient interferometric methods for analyzing bent plates.

Purpose of the Study:

• To propose and validate a compact grating-based shearing interferometer for precise slope measurement of bent plates.
• To develop a mathematical framework for experimental slope determination using the proposed setup.
• To demonstrate the system's efficacy through correlation with theoretical predictions for a cantilever beam.

Main Methods:

• Illumination of the specimen with a collimated laser beam.
• Reflection of light from the specimen through two tandem holographic gratings.
• Superposition of first-order diffracted beams from each grating to generate an interferogram visualizing slope-induced fringes.

Main Results:

• Successful visualization of fringes directly related to the object's slope in the interferogram.
• Mathematical formulation enabling experimental determination of slope values.
• Good correlation between experimentally obtained slope values and theoretical predictions for a cantilever beam.

Conclusions:

• The proposed grating-based shearing interferometer provides an effective and accurate method for slope measurement of bent plates.
• The technique offers a significant advantage in its compact geometric design, eliminating the need for spatial filtering.
• This compact setup enhances the practicality and applicability of grating-based interferometry for structural analysis.