High-precision liquid reference Fizeau interferometry with motionless phase-shifting method and tilt-suppressed...

Area of Science:

• Optical Metrology
• Precision Engineering

Background:

• Traditional Fizeau interferometry faces challenges with surface flatness assumptions and environmental disturbances.
• Liquid surfaces can be affected by factors like edge infiltration, altering their shape over time.

Purpose of the Study:

• To develop a high-precision Fizeau interferometry system utilizing a liquid reference for enhanced measurement accuracy.
• To investigate methods for suppressing tilt errors in interferometric measurements.

Main Methods:

• A motionless temporal polarization phase-shifting method with a liquid crystal variable retarder for stable phase shifting.
• Utilizing 100cSt dimethyl silicone oil as a liquid reference in the interference module.
• Employing the conjugate differential method for orthogonal translation and surface shape acquisition of the liquid reference.

Main Results:

• The liquid reference movement suppresses tilt errors from motorized stage guidance, leveraging liquid properties and gravity.
• Environmental vibrations, mechanical movement, and drift-induced tilt errors are mitigated through averaging and high-precision measurement constraints.
• Experimental results demonstrate a 1.07 nm improvement in the standard deviation of residual vertical diameter lines after calibration.

Conclusions:

• The developed liquid reference Fizeau interferometry system offers superior precision and stability.
• The conjugate differential method effectively addresses liquid surface shape deviations and suppresses tilt errors.
• This approach significantly enhances the accuracy of optical surface metrology.