Fourier plane imaging and illumination-direction-multiplexing using a rotating diffracting element for fourier ptychographic microscopy

We demonstrate a practical method for imaging periodic structures with periods beyond the Rayleigh resolution limit of the imaging system employed. The sample was simultaneously illuminated from several directions using a combination of a source of collimated white-light, a diffracting element, and a microscope objective lens. By rotating the diffracting element, several pairs of real plane and Fourier plane images were obtained. A high-resolution image of the periodic structure was numerically reconstructed by processing the experimental images using the Fourier ptychographic algorithm. We used the Fourier plane imaging microscopy technique to approximate the initial optical disturbance in the phase-recovery algorithm.