Synthetic phase-shifting for optical testing: point-diffraction interferometry without null optics or phase shifters.

Area of Science:

• Optical metrology
• Interferometry
• Wavefront sensing

Background:

• Accurate wavefront characterization is crucial for optical system performance.
• Traditional phase-shifting interferometry often requires multiple measurements and physical phase shifters.
• Non-null testing methods are desirable for large aberrations.

Purpose of the Study:

• To introduce and validate a novel iterative search method, the synthetic phase-shifting (SPS) algorithm.
• To enable maximum-likelihood (ML) estimation of wavefront parameters described by Zernike Fringe polynomials.
• To achieve wavefront estimation from a single interferogram using a point-diffraction interferometer (PDI).

Main Methods:

• Developed the synthetic phase-shifting (SPS) algorithm for iterative wavefront estimation.
• Utilized a point-diffraction interferometer (PDI) to capture a single interferogram.
• Calculated the squared-difference between measured and simulated interferograms to derive phase information.
• Modeled the PDI interferogram, including detector pixel effects.
• Employed a phase-shifting technique without physical phase-shifters.

Main Results:

• The SPS algorithm successfully estimated wavefront coefficients from a single PDI interferogram.
• Computational studies validated the algorithm's performance and identified its constraints.
• Experimental validation using a prototype PDI demonstrated accurate estimation of large wavefront deviations.
• The method operated effectively without the need for null optics or physical phase-shifters.

Conclusions:

• The proposed synthetic phase-shifting (SPS) algorithm offers an innovative approach to wavefront estimation.
• This method provides an accurate and efficient tool for non-null optical testing.
• The technique holds significant potential for advancing optical metrology applications.