Measuring the thickness of soap bubbles with phase-shift interferometry

Area of Science:

• Fluid dynamics
• Optical physics
• Materials science

Background:

• Soap films exhibit complex dynamic behavior, particularly during drainage.
• Accurate measurement of thin film thickness is crucial for understanding fluid dynamics and material properties.
• Interferometry is a powerful tool for non-contact optical measurements.

Purpose of the Study:

• To develop a model for optical path difference in soap bubbles.
• To establish a procedure for extracting global film thickness from interferometric data.
• To analyze film thickness during gravity-driven drainage in the presence of turbulence.

Main Methods:

• Development of a physical model for optical path difference in a soap bubble.
• Application of the model to interferometric data, including phase-shift interferometry.
• Solving for fringe order and defining a procedure for thickness extraction.
• Experimental investigation of soap bubbles under dynamic conditions.

Main Results:

• A validated model for optical path difference in soap bubbles was established.
• A robust procedure was defined to extract global film thickness.
• The method successfully addressed challenges posed by turbulence during drainage.
• Experimental data from single-pass phase-shift interferometry were presented.

Conclusions:

• The proposed model and procedure enable accurate determination of soap bubble film thickness.
• The method is effective even in the presence of turbulent flow during drainage.
• This work provides a valuable tool for studying dynamic thin film phenomena.