PI-FPM: pupil initialization for Fourier ptychographic microscopy directly from measurement data.

Area of Science:

• Computational imaging
• Microscopy techniques
• Optical physics

Background:

• Fourier ptychographic microscopy (FPM) reconstructs high-resolution images by combining multiple low-resolution measurements.
• FPM's performance is sensitive to pupil function initialization during reconstruction.
• Non-convex optimization in FPM requires accurate object and pupil recovery.

Purpose of the Study:

• To introduce a novel pupil-phase initialization method for FPM.
• To improve the convergence stability and reconstruction fidelity of FPM.
• To reduce FPM's reliance on expert calibration and enhance its practical applicability.

Main Methods:

• Developed pupil-initialized FPM (PI-FPM) using standard FPM measurements.
• PI-FPM computes a physically informed pupil-phase initialization before reconstruction.
• Employs Zernike least-squares fitting to estimate low-order aberrations from lateral image shifts.

Main Results:

• PI-FPM demonstrated improved convergence stability and reconstruction fidelity in synthetic and real experiments.
• Achieved up to 8 dB PSNR gains and robust performance under significant aberrations (up to 2π radians RMS).
• Showed particular robustness in outer field regions, crucial for large-field imaging.

Conclusions:

• PI-FPM enhances FPM's practical applicability by simplifying calibration.
• The method is hardware-agnostic and algorithm-independent, allowing retroactive use on existing data.
• PI-FPM significantly improves the routine use of FPM in real-world scenarios like whole-slide imaging.