查看更多>>摘要：Polarization parametric indirect microscopic imaging (PIMI) can obtain anisotropic nanoscale structural information of the sample by utilizing a polarization modulated illumination scheme and fitting the far-field variation of polarization states of the scattered photons. The rich scattering information of PIMI images can be exploited for identification of viral particles, aiming for early infection screening of viruses. Accurate processing and analysis of PIMI results is an important step for obtaining structural feature information of virus. However, the systematic noise, mainly caused by the mechanical or electrical disturbance from the modulation of the illumination when taking raw images, fairly degrades the image resolution and contrast, making the analysis of results more time-consuming with higher error rate. To achieve efficient noise suppressing in the obtained PIMI images, we developed a neural network-based framework of algorithms. A fairly effective denoising method particularly for PIMI imaging was proposed based on a U-Net. From both the numerical and experimental results, the developed method significantly improves the quality of PIMI images with the best capability of noise removal compared with the traditional denoising algorithms and other neural network architecture. This method can be employed as a fixed preprocessing procedure of raw PIMI images, which is greatly helpful to realize rapid, accurate and programmed analysis of results in PIMI applications.
查看更多>>摘要：Dispersive interferometry based on optical frequency combs has been widely applied in long-distance ranging, refractive index measurements of solids, and optical coherence tomography. In this study, we propose a theoretical model to analyze the influence of spectral resolution that can explain the relationship between the interference contrast of the interference spectrum and the variation in the measured distance with the resolution of a spectrometer. It can also be used to compensate for the systematic error caused by the resolution of the spectrometer. Our proposed model was verified experimentally, and the relative difference between the experimental and the theoretical results was less than 0.003%.
查看更多>>摘要：We demonstrate that the conservation of extremal ellipticity for an astigmatic Gaussian beam propagating in a rotationally invariant medium, for example, an arbitrary sequence of free space propagation and stigmatic lenses, initially identified by Lo et al. (2017), is a direct consequence of the conservation of orbital angular momentum (OAM) of the beam. We derive explicit analytical expressions for the first few non-zero moments of the beam OAM and show that, apart from fundamental constants, they depend only on the beam's extremal ellipticity. This unexpected connection uncovers the actual origin of a new propagation invariant, namely extremal ellipticity, for a broad class of coherent, single-mode Gaussian beams. We expect this principle to find use in various applications where spot circularity along an extended region of the beam is essential; such as laser micromachining, imaging, optical trapping, and inertial confinement fusion.
NSTL
Elsevier