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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Image formation in coronagraphs due to mirror polarization aberrations

Chipman, Russell A. 27 November 2017 (has links)
The PSF for astronomical telescopes and instruments depends not only on geometric wavefront aberrations, but also on those polarization aberrations from the polarization properties of reflecting and transmitting surfaces. The image plane irradiance distribution is the linear superposition of four PSF images: one for each of the two orthogonal polarizations and one for each of two cross-coupled polarization terms.
2

Advances in modeling polarimeter performance

Chipman, Russell A. 30 August 2017 (has links)
Artifacts in polarimeters are apparent polarization features which are not real but result from the systematic errors in the polarimeter. The polarization artifacts are different between division of focal plane, spectral, and time modulation polarimeters. Artifacts result from many sources such as source properties, micropolarizer arrays, coatings issues, vibrations, and stress birefringence. A modeling examples of polarization artifacts due to a micro-polarizer array polarimeter is presented.
3

Challenges in coronagraph optical design

Chipman, Russell A. 06 September 2017 (has links)
The point spread function (PSF) for astronomical telescopes and instruments depends not only on geometric aberrations and scalar wave diffraction, but also on the apodization and wavefront errors introduced by coatings on reflecting and transmitting surfaces within the optical system. Geometrical ray tracing provides incomplete image simulations for exoplanet coronagraphs with the goal of resolving planets with a brightness less than 10<^>-9 of their star located within 3 Airy disk radii. The Polaris-M polarization analysis program calculates uncorrected coating polarization aberrations couple around 10<^>-5 light into crossed polarized diffraction patterns about twice Airy disk size. These wavefronts not corrected by the deformable optics systems. Polarization aberrations expansions have shown how image defects scale with mirror coatings, fold mirror angles, and numerical aperture.

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