High numerical aperture Fourier ptychography: principle, implementation and characterization.

Area of Science:

• Microscopy
• Optical Engineering
• Computational Imaging

Background:

• Bright-field microscopes have limitations in resolution tied to their objective lens numerical aperture (NA).
• Fourier ptychography (FP) is a computational imaging technique that can overcome these limitations.

Purpose of the Study:

• To investigate the effectiveness of Fourier ptychography in enhancing the resolution of bright-field microscopes.
• To synthesize a high numerical aperture (NA) system using a lower NA objective lens and FP.

Main Methods:

• An FP microscope (FPM) was constructed using a 40X 0.75NA objective lens.
• Illumination control and computational post-processing were employed to synthesize a system NA of 1.45.
• Resolution was assessed using a two-slit target at a wavelength of 632 nm.

Main Results:

• The synthesized system achieved a two-slit resolution of 335 nm.
• This resolution is comparable to a standard 1.25 NA oil immersion microscope (315 nm).
• The achieved resolution closely matched theoretical predictions.

Conclusions:

• Fourier ptychography effectively extends the resolution-performance of bright-field microscopes.
• FP allows for the use of lower NA objectives to achieve high-resolution imaging.
• This technique offers potential for improved working distance and field-of-view in microscopy.