Abstract
In this paper, an irregular displacement-based lensless wide-field microscopy imaging platform is presented by combining digital in-line holography and computational pixel super-resolution using multi-frame processing. The samples are illuminated by a nearly coherent illumination system, where the hologram shadows are projected into a complementary metal-oxide semiconductor-based imaging sensor. To increase the resolution, a multi-frame pixel resolution approach is employed to produce a single holographic image from multiple frame observations of the scene, with small planar displacements. Displacements are resolved by a hybrid approach: (i) alignment of the LR images by a fast feature-based registration method, and (ii) fine adjustment of the sub-pixel information using a continuous optimization approach designed to find the global optimum solution. Numerical method for phase-retrieval is applied to decode the signal and reconstruct the morphological details of the analyzed sample. The presented approach was evaluated with various biological samples including sperm and platelets, whose dimensions are in the order of a few microns. The obtained results demonstrate a spatial resolution of 1.55 µm on a field-of-view of ≈30 mm2.
Highlights
Microscale imaging in life sciences so far has been associated with conventional light microscopes using geometric optic[1]
Lensless imaging technologies present great impact on the development of portable POC platforms for resource-limited settings, and by associating them with computational pattern recognition and digital image-processing techniques, novel platform technologies are developed for real world applications
The presented portable lensless wide-field microscopy platform is one example for such applications, where both imaging sensors and computational image interpretation are integrated on the same platform for micron analysis
Summary
Microscale imaging in life sciences so far has been associated with conventional light microscopes using geometric optic[1]. The advent of the holography principle, in 1948 by Dennis Gabor[2], allowed the development of electron microscopes with high-resolution (HR), opening a wide range of investigation for both microscale and nanoscale microscopy Such optical instruments, may require advanced infrastructure, being mostly restricted to well-established institutes. By using a coherent light-source (i.e., monochromatic wave), the spatial signatures are converted to pattern interferences of the analyzed sample, and holographic information is obtained according to the scalar diffraction theory. By utilizing this pattern, numerical methods for phaseretrieval can be used to reconstruct the morphological details of the sample at specific object-planes
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