Optical image reconstruction in 4 f imaging system: Role of spatial coherence structure engineering

We examine the effect of spatial coherence on the image quality of a classic 4f imaging system when its Fourier plane is partially blocked by an opaque obstacle. We find that although reducing the degree of spatial coherence of the source results in the improved image quality, the concurrent distortions in the image plane are inevitable. Employing a suitable decomposition of a partially coherent light source into a set of coherent pseudo-modes with a multitude of linear phase shifts, we demonstrate that the distortions are primarily induced by the modes whose maxima are located at the obstacle edges. We show that by tailoring spatial coherence of the source we can enable all the coherent modes to circumnavigate the obstacle, ensuring the same image quality as if the obstacle were absent from the Fourier plane. We expect our findings to be instrumental in high-contrast optical microscopy with coherence structured light.