Super-resolution imaging within reach

Although several optical techniques have been recently developed in order to overcome the resolution limit in microscopy, the imaging of sub-wavelength features is still a real challenge. In practise, super-resolution techniques remain difficult to build or are photo-toxic for the biological samples. However, microsphere-assisted microscopy has recently made super-resolution imaging accessible to scientists (e.g. optical metrologists, engineers and biologists). This paper presents an easy-to-implement optical setup to perform full-field and contactless super-resolution measurements of nanostructured media or biological elements. For this purpose, a classical microscope was enhanced by introducing a transparent microsphere. We show that this rather simple approach makes it possible to achieve a lateral resolution of 200 nm in air, i.e. the visualization of feature sizes of 100 nm

Colon phantoms with cancer lesions for endoscopic characterization with optical coherence tomography

International audienceOptical coherence tomography (OCT) is a growing imaging technique for real-time early diagnosis of digestive system diseases. As with other well-established medical imaging modalities, OCT requires validated imaging performance and standardized test methods for performance assessment. A major limitation in the development and testing of new imaging technologies is the lack of models for simultaneous clinical procedure emulation and characterization of healthy and diseased tissues. Currently, the former can be tested in large animal models and the latter can be tested in small animal disease models or excised human biopsy samples. In this study, a 23 cm by 23 cm optical phantom was developed to mimic the thickness and near-infrared optical properties of each anatomical layer of a human colon, as well as the surface topography of colorectal polyps and visual appearance compatible with white light endoscop

Transmission Microsphere-Assisted Dark-Field Microscopy

Microsphere-assisted microscopy allows the limit of the diffraction of light to overcome while being non-invasive, full-field, label-free, and easy-to-implement. However, the observation of translucent samples remains difficult using a classical bright-field illumination. In this work, a method is presented for the inspection of quasi-transparent sub-diffraction-limited structures by using dark-field illumination in the transmission mode. Glass-imprint features, having a size of 250 nm, as well as fixed mouse brain cells have been visualized using the dark-field microsphere-assisted technique. The possibility to observe feature sizes up to 100 nm has been demonstrated in air using a 25-mu m-diameter glass microsphere combined with an optical microscope, opening new possibilities for biological imaging