Spatial coherence beam fundamentals: the Wigner distribution and the triple correlation function

1999 ◽  
Author(s):  
Roman Castaneda ◽  
Francisco F. Medina-Estrada
2015 ◽  
Author(s):  
Tobias Mey ◽  
Bernd Schäfer ◽  
Klaus Mann ◽  
Barbara Keitel ◽  
Elke Plönjes ◽  
...  

Author(s):  
Sheng-Zhou Qiang ◽  
Xian Jiang ◽  
Pu-Yu Han ◽  
Xi-Ya Shi ◽  
An-Yang Wu ◽  
...  

AbstractLinear canonical transform (LCT) is a powerful tool for improving the detection accuracy of the conventional Wigner distribution (WD). However, the LCT free parameters embedded increase computational complexity. Recently, the instantaneous cross-correlation function type of WD (ICFWD), a specific WD relevant to the LCT, has shown to be an outcome of the tradeoff between detection accuracy and computational complexity. In this paper, the ICFWD is applied to detect noisy single component and bi-component linear frequency-modulated (LFM) signals through the output signal-to-noise ratio (SNR) inequality modeling and solving with respect to the ICFWD and WD. The expectation-based output SNR inequality model between the ICFWD and WD on a pure deterministic signal added with a zero-mean random noise is proposed. The solutions of the inequality model in regard to single component and bi-component LFM signals corrupted with additive zero-mean stationary noise are obtained respectively. The detection accuracy of ICFWD with that of the closed-form ICFWD (CICFWD), the affine characteristic Wigner distribution (ACWD), the kernel function Wigner distribution (KFWD), the convolution representation Wigner distribution (CRWD) and the classical WD is compared. It also compares the computing speed of ICFWD with that of CICFWD, ACWD, KFWD and CRWD.


2014 ◽  
Vol 22 (13) ◽  
pp. 16571 ◽  
Author(s):  
Tobias Mey ◽  
Bernd Schäfer ◽  
Klaus Mann ◽  
Barbara Keitel ◽  
Marion Kuhlmann ◽  
...  

Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.


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