Improved resolution Fourier ptychography scheme using oil-filled dome-shaped LED array

Abstract

Utilising angular-varied illumination in Fourier Ptychography, the resolution of optical microscopes can be increased and the phase of the sample can also be recovered while maintaining a wide field-of-view. In this work, an Fourier Ptychography microscopy imaging setup is demonstrated using a 10X 0.28 NA objective lens and a dome-shaped light-emitting diode array illuminator. By increasing the refractive index of the medium between the sample and light sources using oil filled dome, a synthetic system numerical aperture of 0.68 is achieved using only 37 light-emitting diodes. The measured resolution of 345 nm at a wavelength of 530 nm closely matches the theoretical prediction. Furthermore, the results of the oil-medium illumination are compared to free-space illumination. The oil immersion on the illumination side effectively enhances the illumination numerical aperture as compared to air and reduces the need for far off-axis light-emitting diodes. The result is high-resolution Fourier Ptychography imaging with relatively fewer light-emitting diodes providing both short capture and reconstruction times.