Interferometric measurement of surface shape by wavelength tuning suppressing random intensity error

Area of Science:

• Optical Metrology
• Interferometry
• Surface Characterization

Background:

• Phase-shifting algorithms are crucial for high-accuracy optical surface measurements.
• Conventional algorithms exhibit susceptibility to random intensity errors, limiting measurement precision.
• Minimizing these errors is essential for advanced optical metrology applications.

Purpose of the Study:

• To formulate and estimate the susceptibility of phase-shifting algorithms to random intensity errors.
• To develop a novel phase-shifting algorithm that minimizes random intensity errors.
• To experimentally validate the performance of the developed algorithm in surface shape measurement.

Main Methods:

• Formulation and estimation of random intensity error susceptibility in phase-shifting algorithms.
• Development of the 7N-6 phase-shifting algorithm utilizing characteristic polynomial theory.
• Surface shape measurement of a transparent wedge plate using a wavelength-tuning Fizeau interferometer and the 7N-6 algorithm.

Main Results:

• The susceptibility of conventional windowed phase-shifting algorithms to random intensity error was analyzed.
• The 7N-6 phase-shifting algorithm was successfully developed to mitigate random intensity errors.
• Experimental measurement of a transparent wedge plate achieved a surface shape accuracy of 2.5 nm.

Conclusions:

• The 7N-6 phase-shifting algorithm effectively minimizes random intensity errors in optical metrology.
• The developed algorithm significantly enhances surface shape measurement accuracy for optical components.
• This research contributes to advancing precision in optical surface characterization.