Topic
Angular aperture
About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.
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Patent•
09 Jul 2015
TL;DR: In this article, a tunable acoustic gradient index of refraction (TAG) lens is operated at different focal length scanning frequencies depending on the magnification state, which provides a relatively consistent range of focus with various magnification lenses, without limiting the effective numerical aperture of the imaging system.
Abstract: An imaging system is provided for a precision machine vision inspection or metrology system. The imaging system optical path includes a variable magnification lens portion and a variable focal length lens portion. The variable magnification lens portion includes various magnification states (e.g., 0.5× to 100×, using interchangeable lenses, or the like.) The variable focal length lens portion (e.g., including a tunable acoustic gradient index of refraction (“TAG”) lens) is operated at different focal length scanning frequencies depending on the magnification state. A TAG lens operated in this manner provides a relatively consistent range of focus (e.g., corresponding to a number of depths of field) with various magnification lenses, without limiting the effective numerical aperture of the imaging system.
18 citations
TL;DR: The modulation transfer function is calculated for imaging with linearly, circularly and radially polarized light as well as for different numerical apertures and aperture shapes and it is shown that in the latter case zeros of the MTF may appear which are purely due to polarization effects and which depend on the aperture angle.
Abstract: The modulation transfer function (MTF) is calculated for imaging with linearly, circularly and radially polarized light as well as for different numerical apertures and aperture shapes. Special detectors are only sensitive to one component of the electric energy density, e.g. the longitudinal component. For certain parameters this has advantages concerning the resolution when comparing to polarization insensitive detectors. It is also shown that in the latter case zeros of the MTF may appear which are purely due to polarization effects and which depend on the aperture angle. Finally some ideas are presented how to use these results for improving the resolution in lithography.
18 citations
TL;DR: Gbur et al. as mentioned in this paper showed that the spectral splitting phenomenon near phase singularities of focused waves disappears when the numerical aperture is higher than critical values that are different between the incident polarization direction and the axial direction.
Abstract: We demonstrate that because of the depolarization effect associated with a high-numerical-aperture lens, the recently predicted spectral splitting phenomenon near phase singularities of focused waves [G. Gbur, T. D. Visser, and E. Wolf, Phys. Rev. Lett. 88, 013901 (2002)] disappears when the numerical aperture is higher than critical values that are different between the incident polarization direction and the axial direction.
18 citations
TL;DR: In this article, a subwavelength circular aperture is replaced by uniform magnetic currents and charges and the model allows one to obtain the normalized cross section for the aperture radius up to half of the wavelength, which exceeds the 0.2 wavelength limit of the Bethe-Bouwkamp model.
Abstract: Diffraction of normally incident light by a subwavelength circular aperture is calculated analytically. The aperture is opened on a perfectly conducting planar screen with infinitesimal thickness. In our model, the aperture is replaced by uniform magnetic currents and charges. The model allows one to obtain the normalized cross section for the aperture radius up to half of the wavelength, which exceeds the 0.2 wavelength limit of the Bethe-Bouwkamp's dipole model [1-3]. Also, in addition to reproducing the (ka)4 dependence, which is characteristic of the dipole mode, our uniform field model explains the transmission enhancement obtained in Abajo's numerical simulation [4].
18 citations
Patent•
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24 Dec 1990
TL;DR: In this paper, a radial GRIN lens element having a concave surface on the image side and a positive refractive power at the most image side location in the third lens component was designed to have a high aperture ratio and favorably corrected coma.
Abstract: An imaging lens system comprising, in the order from the object side, a first lens component having a convex surface on the object side and a positive refractive power, a second lens component having a concave surface on the image side and a negative refractive power, and a third lens component. Through the imaging lens system is of a triplet or Tessar type, the lens system is designed so as to have a high aperture ratio and favorably corrected coma by arranging a radial GRIN lens element having a concave surface on the image side and a positive refractive power at the most image side location in the third lens component.
18 citations