Topic
Bessel filter
About: Bessel filter is a research topic. Over the lifetime, 656 publications have been published within this topic receiving 16808 citations.
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21 Mar 1975TL;DR: In this article, a video traveling matte system is described in which the video signal from a foreground television camera is examined for the presence of a particular color by an arrangement employing multipliers to multiply the differences between the red and blue components of video signal and a luminance signal derived from the video signals by the signals from a sine/cosine potentiometer.
Abstract: A video traveling matte system is disclosed in which the video signal from a foreground television camera is examined for the presence of a particular color by an arrangement employing multipliers to multiply the differences between the red and blue components of the video signal and a luminance signal derived from the video signal by the signals from a sine/cosine potentiometer. The combined signal from the outputs of the multipliers is fed to a first comparator for comparison with a reference value, and the resulting pulses are filtered by a 4-pole active Bessel filter and compared with a reference value in a second comparator to increase the width of the pulses by a selected amount. The pulses of increased width prevent the formation of a matte outline between foreground and background images as the true and complementary values thereof are applied to alternately gate the video signals from the foreground television camera and a background television camera to a common output. The effects of shadows in the foreground image are maintained despite substitution of the background image by utilizing the combined signal from the multipliers to modulate pulses from the second comparator prior to use of such pulses to gate the video signal from the background television camera to the common output. The effects of shadows are further enhanced by a logarithmic amplifier which introduces a predetermined logarithmic transfer characteristic into the modulation signal to compensate for the black stretch circuits used in most television cameras.
21 citations
TL;DR: An exact solution of expansion coefficients for a T-matrix method interacting with acoustic scattering of arbitrary order Bessel beams from an obstacle of arbitrary location is derived analytically.
Abstract: An exact solution of expansion coefficients for a T-matrix method interacting with acoustic scattering of arbitrary order Bessel beams from an obstacle of arbitrary location is derived analytically. Because of the failure of the addition theorem for spherical harmonics for expansion coefficients of helicoidal Bessel beams, an addition theorem for cylindrical Bessel functions is introduced. Meanwhile, an analytical expression for the integral of products including Bessel and associated Legendre functions is applied to eliminate the integration over the polar angle. Note that this multipole expansion may also benefit other scattering methods and expansions of incident waves, for instance, partial-wave series solutions.
21 citations
TL;DR: This work considers a way of obtaining a narrower diameter of the central core of a diffractive pattern generated by the Bessel beams by superposition of two or more Bessel beam with appropriately chosen amplitudes and widths.
Abstract: The characteristic dimensions of Bessel beams are fully determined by the corresponding Bessel functions. We consider a way of obtaining a narrower diameter of the central core of a diffractive pattern generated by the Bessel beams. The method relies on superposition of two or more Bessel beams with appropriately chosen amplitudes and widths. The disturbing influence of the aperture's edges can be eliminated by addition of the proper amplitude filter.
21 citations
TL;DR: In this article, the semi-group density and the generalized Bessel function and the W-invariant generalized Hermite polynomials were derived for dihedral systems.
Abstract: We are interested in radial Dunkl processes associated with dihedral systems. We write down the semi-group density and as a by-product the generalized Bessel function and the W-invariant generalized Hermite polynomials. Then, a skew product decomposition, involving only independent Bessel processes, is given and the tail distribution of the first hitting time of boundary of the Weyl chamber is computed.
21 citations
25 Mar 2015
TL;DR: In this paper, the point spread function depending on the spectral filter parameters is estimated by decomposition of the incident radiation on vector Bessel modes, and it is shown that significant deterioration in resolution occurs only in wide-angle optical systems.
Abstract: The article is devoted to hyperspectrometer modeling based on the use of filters with linearly varying parameters. The point spread function depending on the spectral filter parameters is estimated. The results were obtained by decomposition of the incident radiation on vector Bessel modes. Numerical calculations show that significant deterioration in resolution occurs only in wide-angle optical systems
21 citations