Wide-field interferometric microscopy is a common-path interferometry technique that allows for label-free and high-throughput detection of weakly scattering sub-diffraction-limited biological nanoparticles. Such nanoparticles appear as diffraction-limited-spots in the image and optically resolving them beyond their ‘digital’ detection still remains a challenge owing to the diffraction barrier as well as the typical signal levels that fall below the noise floor. In this study, we demonstrate the utility of computational optics in the interference enhanced nanoparticle imaging to improve its resolving power to obtain structural information on clinically relevant and often complexed-shaped biological nanoparticles such as viruses and exosomes. We consider a spatially incoherent structured illumination based image reconstruction strategy in wide-field interferometric microscopy to achieve high contrast nanoparticle imaging with super-resolution. Our reconstruction technique makes use of the optical transfer function of the system derived via an analytical model based on angular spectrum representation. We provide experimental demonstrations using an artificial sample to quantify the resolution enhancement as well as a biological sample for concept demonstration. We also benchmark the results against gold standard images obtained using an electron microscope. Our highly-sensitive super-resolution imaging system constitutes a noncomplex optical design, which can be realized with simple modifications to a conventional epi-illumination microscope, offering a cost-effective alternative to the laborious and expensive standard high-resolution microscopy techniques. It has a broad spectrum of applications ranging from clinical diagnostics to biotechnological research.
Oguzhan Avci, Celalettin Yurdakul, Derin D. Sevenler, Fulya E. Kanik, Alex C. Matlock, Lei Tian, and M. Selim Ünlü, "Reconstruction in wide-field interferometric microscopy for imaging weakly scattering biological nanoparticles with super-resolution (Conference Presentation)," Proc. SPIE 10510, Frontiers in Biological Detection: From Nanosensors to Systems X, 105100J (Presented at SPIE BiOS: January 29, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2290259.5751636873001.
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