Simultaneous high-resolution and wide-field microscopy with improved image sharpness using pseudo-thermal light source and Fourier Ptychography

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Lasers have been widely used in areas such as interferometry, imaging, holography, projection displays, etc. as they provide the benefit of high spatio-temporal coherence and high brightness along with the formation of speckles. High spatio-temporal coherence is a remarkable property of laser due to which interferometry and holography can be easily implemented, but the occurrence of spurious fringes due to multiple reflections and the formation of speckles reduces the quality of images in laser-based systems. Here, we present the implementation of Fourier Ptychography using pseudo-thermal light source. The spatial and temporal coherence properties of laser light have been reduced using a static and rotating diffuser leading to the implementation of pseudo-thermal light source. The use of pseudo-thermal source leads to an increase in image sharpness and decrease in speckle contrast thus acting as a suitable source for imaging. The improvement in experimental results suggests that both high temporal coherence and low spatial coherence is necessary for high contrast imaging with improvement in spatial resolution. The pseudo-thermal light source acts as a solution to non-uniform illumination with higher sharpness and higher brightness compared to spatially and temporally incoherent LED array light source. Experiments have been carried out on biological samples to prove the effect.