Interfacial shape and contact-angle measurement of transparent samples with confocal interference microscopy

Area of Science:

• Optical physics
• Microscopy techniques
• Materials science

Background:

• Confocal interference microscopy is crucial for high-resolution imaging.
• Accurate optical path length (OPL) measurement is essential for analyzing refractive specimens.
• Refractive errors can significantly impact OPL measurements in microscopy.

Purpose of the Study:

• To develop a predictive model for effective optical path length in thick, refractive specimens.
• To correct phase measurements for refractive errors using an iterative algorithm.
• To validate the model and algorithm with experimental measurements.

Main Methods:

• Developed a model considering the finite diameter of the confocal microscope's pinhole.
• Incorporated the model into an iterative algorithm for phase correction.
• Validated the algorithm using a reflected-light microscope with a phase-shifting laser-feedback interferometer.

Main Results:

• The model accurately predicts effective OPL through refractive specimens on reflective substrates.
• The iterative algorithm successfully corrected for refractive errors in phase measurements.
• Experimental validation confirmed the model's efficacy in measuring interface shape and contact angles.

Conclusions:

• The developed model and algorithm provide a robust method for accurate OPL determination in confocal interference microscopy.
• This approach enhances the analysis of complex sample geometries and material properties.
• The validated method has practical applications in materials science and surface analysis.