![]() However, in DHM, it is consistently possible to be numerically focused on the image plane post-recording of the digital hologram to achieve the best possible imaging quality 27. Another challenging issue in MAM that can be less important in microsphere-assisted DHM is precise positioning of the MS and in some cases preserving the relative sample-to-microsphere distance 26 during the imaging. To this end, phase information of the reference hologram (taken for no-sample state in the setup) is subtracted from the object phase during the numerical reconstruction process 25. However, in DHM, thanks to the phase compensation possibility, the effect of any possible contaminations and aberrations in the optical train on the final data can be removed. It also brings about a curved deformation in the measured phase in interference microscopy, which in turn further sacrifices the effective field-of-view (FoV) 13. Adding a spherical lens to a conventional microscope introduces non-negligible spherical aberrations 1. On the other hand, MAM benefits from DHM’s advantageous features. The advantages of MAM over other resolution enhancement techniques for DHM are further featured 22, 23 in MAM, due to the symmetric structure of the MS, the resolution enhancement is achieved simultaneously in all spatial directions, which is extremely important in real-time imaging of specimens with rapid dynamics 12, 24. Microsphere-assisted interference microscopy provides an inexpensive and non-destructive imaging technique for 3D surface metrology 17, 20 and microsphere-assisted digital holographic microscopy (DHM) brings forward a cost-effective and easy-to-implement high-quality quantitative phase imaging approach in transmission and reflection modes 21. Additionally, MAM has shown its potential to be easily integrated with other resolution-enhancing schemes, such as structured and oblique illumination, to achieve even further resolution enhancements in 3D microscopy systems 18, 19. However, MAM combined with interferometric setups has shown promising results in producing 3D label-free images with enhanced lateral resolution. Although interferometric arrangements have significantly higher axial resolution compared to conventional microscopy, their lateral resolution would still be restricted by the diffraction limit. MAM has well matched up with interferometric-based approaches, such that both have benefited from each other’s features. This can be simply achieved in an interferometric arrangement, by placing the MS within the working distance of either a conventional objective lens 10, 11, 12, 13, 14, 15 or a dedicated interferometric objective lens (Fig. MAM can also be extended to interference and digital holographic microscopies for 3D imaging with enhanced resolution. MAM is a versatile technique and can be incorporated with different microscopes, such as fluorescent 6, 7, confocal 8, and two-photon 9 setups. The latter approach would allow fabrication of novel resolution-improving optical devices 5. MAM can be performed with low-index ( n~1.5) MSs 2 as well as high-index ( n > 1.9) MSs 3 placed in a background medium with a lower refractive index than that of the microsphere 4. ![]() Focusing the objective lens on the virtual image formed underneath the specimen by the MS enables microscopy with higher resolution and magnification compared to using the objective lens without the MS ( θ 2 > θ 1 in Fig. MAM is a simple, yet efficient approach in which a microsphere (MS) is placed in the immediate vicinity of a specimen, as schematically shown in Fig. It has been shown in the past decade that micron-scale dielectric spheres and cylinders can be used as supplementary lenses to improve microscopy resolution, a technique termed “microsphere-assisted microscopy” (MAM) 1.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |