Analytical formulas for the cross-spectral density matrix of stochastic electromagnetic Gaussian Schell-model (EGSM) beams passing through an astigmatic optical system are derived. We show both analytically and by numerical examples the effects of astigmatism on spectra, coherence and polarization of stochastic electromagnetic EGSM beams propagating through an astigmatic lens. A comparison with the aberration-free case is made, and shows that the astigmatism has significant effect on the spectra, coherence and polarization.
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http://dx.doi.org/10.1364/oe.17.007310 | DOI Listing |
J Struct Biol
March 2024
Department of Molecular, Cellular, and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, United States. Electronic address:
Ctfplotter in the IMOD software package is a flexible program for determination of CTF parameters in tilt series images. It uses a novel approach to find astigmatism by measuring defocus in one-dimensional power spectra rotationally averaged over a series of restricted angular ranges. Comparisons with Ctffind, Gctf, and Warp show that Ctfplotter's estimated astigmatism is generally more reliable than that found by these programs that fit CTF parameters to two-dimensional power spectra, especially at higher tilt angles.
View Article and Find Full Text PDFFemtosecond laser filamentation propagating tens of meters to several kilometers with high intensity in the atmosphere has been demonstrated as a powerful tool for remote sensing. In contrast to the refractive systems, the reflective optical systems possess a variety of advantages including broad bandwidth, large aperture, light weight and low energy loss. However, astigmatic aberration is inevitably introduced by off-axis reflective mirrors.
View Article and Find Full Text PDFOptica
June 2019
Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60201, USA.
Spectroscopic single-molecule localization microscopy (sSMLM) captures the full emission spectra of individual molecules while simultaneously localizing their spatial locations at a precision greatly exceeding the optical diffraction limit. To achieve this, sSMLM uses a dispersive optical component to separate the emitted photons into dedicated spatial and spectral imaging channels for simultaneous acquisition. While adding a cylindrical lens in the spatial imaging channel enabled three-dimensional (3D) imaging in sSMLM, the inherent astigmatism leads to technical hurdles in spectral calibration and nonuniform lateral resolution at different depths.
View Article and Find Full Text PDFA double-channel prism imaging spectrometer that includes visible-near-infrared (VNIR) and shortwave-infrared (SWIR) spectra is presented. Double slits divide a wide spectral band into two independent channels for VNIR and SWIR, guaranteeing their independent spectral resolution. A beam splitter splits the band into two, one detected by the SWIR and the other by the VNIR detector.
View Article and Find Full Text PDFSpectrochim Acta A Mol Biomol Spectrosc
June 2018
Department of Physics, Hal Marcus College of Sciences and Engineering, University of West Florida, Pensacola, FL 32514, USA. Electronic address:
We report the construction and characterization of a coherent Raman tabletop system utilizing a novel astigmatic optical focusing geometry, a broadband nanosecond optical parametric oscillator and volumetric Bragg filters assisting 3CBCRS measuring system for the first time. In order to illustrate the versatility of the measurements and reveal the molecular information obtainable, two well-characterized chemicals were selected. Polarization sensitive epi-detected 3CBCRS spectra of liquid CCl and calcite crystal were recorded and analyzed.
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