scholarly journals Controlling spatial coherence with an optical complex medium

2021 ◽  
Author(s):  
Alfonso Nardi ◽  
Felix Tebbenjohanns ◽  
Massimiliano Rossi ◽  
Shawn Divitt ◽  
Andreas Norrman ◽  
...  
Keyword(s):  
Spatial Coherence ◽  
Complex Medium

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

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.

An Alternate Algorithm for (3x3) Median Filtering of Digital Images

2012 ◽  
Vol 2 (1) ◽  
pp. 7-9 ◽  
Author(s):  
Satinderjit Singh
Keyword(s):  
Median Filter ◽  
Computational Cost ◽  
Spatial Coherence ◽  
General Purpose ◽  
Median Filtering ◽  
Basic Algorithm ◽  
Temporal Complexity ◽  
Filter Kernel ◽  
One Step ◽  
High Computational Cost

Median filtering is a commonly used technique in image processing. The main problem of the median filter is its high computational cost (for sorting N pixels, the temporal complexity is O(N·log N), even with the most efficient sorting algorithms). When the median filter must be carried out in real time, the software implementation in general-purpose processorsdoes not usually give good results. This Paper presents an efficient algorithm for median filtering with a 3x3 filter kernel with only about 9 comparisons per pixel using spatial coherence between neighboring filter computations. The basic algorithm calculates two medians in one step and reuses sorted slices of three vertical neighboring pixels. An extension of this algorithm for 2D spatial coherence is also examined, which calculates four medians per step.

Light intensity and spatial coherence characteristics of laser coherent detection in a turbulent atmosphere

2020 ◽  
Vol 13 (4) ◽  
pp. 728-736
Author(s):  
REN Jian-ying ◽  
◽  
◽  
SUN Hua-yan ◽  
ZHAO Yan-zhong ◽  
...  
Keyword(s):  
Light Intensity ◽  
Turbulent Atmosphere ◽  
Spatial Coherence ◽  
Coherent Detection

scholarly journals Optical coherence encryption with structured random light

PhotoniX ◽  
2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Deming Peng ◽  
Zhaofeng Huang ◽  
Yonglei Liu ◽  
Yahong Chen ◽  
Fei Wang ◽  
...  
Keyword(s):  
Fractional Fourier Transform ◽  
Spatial Coherence ◽  
Second Order ◽  
Statistical Characteristics ◽  
Interference Effects ◽  
Complex Environments ◽  
Optical Encryption ◽  
Light Matter Interaction ◽  
Encryption Method ◽  
Promising Avenue

AbstractInformation encryption with optical technologies has become increasingly important due to remarkable multidimensional capabilities of light fields. However, the optical encryption protocols proposed to date have been primarily based on the first-order field characteristics, which are strongly affected by interference effects and make the systems become quite unstable during light–matter interaction. Here, we introduce an alternative optical encryption protocol whereby the information is encoded into the second-order spatial coherence distribution of a structured random light beam via a generalized van Cittert–Zernike theorem. We show that the proposed approach has two key advantages over its conventional counterparts. First, the complexity of measuring the spatial coherence distribution of light enhances the encryption protocol security. Second, the relative insensitivity of the second-order statistical characteristics of light to environmental noise makes the protocol robust against the environmental fluctuations, e.g, the atmospheric turbulence. We carry out experiments to demonstrate the feasibility of the coherence-based encryption method with the aid of a fractional Fourier transform. Our results open up a promising avenue for further research into optical encryption in complex environments.

scholarly journals Ultracold atom interferometry in space

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Maike D. Lachmann ◽  
Holger Ahlers ◽  
Dennis Becker ◽  
Aline N. Dinkelaker ◽  
Jens Grosse ◽  
...  
Keyword(s):  
Spatial Coherence ◽  
Free Fall ◽  
Atom Interferometry ◽  
Matter Wave ◽  
Sounding Rocket ◽  
Ultracold Atom ◽  
Fundamental Physics ◽  
Light Pulses ◽  
Bose Einstein ◽  
Promising Source

AbstractBose-Einstein condensates (BECs) in free fall constitute a promising source for space-borne interferometry. Indeed, BECs enjoy a slowly expanding wave function, display a large spatial coherence and can be engineered and probed by optical techniques. Here we explore matter-wave fringes of multiple spinor components of a BEC released in free fall employing light-pulses to drive Bragg processes and induce phase imprinting on a sounding rocket. The prevailing microgravity played a crucial role in the observation of these interferences which not only reveal the spatial coherence of the condensates but also allow us to measure differential forces. Our work marks the beginning of matter-wave interferometry in space with future applications in fundamental physics, navigation and earth observation.

scholarly journals Genetic analysis of temperature-sensitive lethal mutants of Salmonella typhimurium.

Genetics ◽  
1989 ◽  
Vol 123 (4) ◽  
pp. 625-633 ◽  
Author(s):  
M B Schmid ◽  
N Kapur ◽  
D R Isaacson ◽  
P Lindroos ◽  
C Sharpe
Keyword(s):  
High Temperature ◽  
Genetic Analysis ◽  
Salmonella Typhimurium ◽  
Complex Medium ◽  
Temperature Sensitive ◽  
Nonpermissive Temperature ◽  
Anaerobic Conditions ◽  
Temperature Growth ◽  
Lethal Phenotype ◽  
Lethal Mutations

Abstract We have isolated 440 mutants of Salmonella typhimurium that show temperature-sensitive growth on complex medium at 44 degrees. Approximately 16% of the mutations in these strains have been mapped to 17 chromosomal locations; two of these chromosomal locations seem to include several essential genes. Genetic analysis of the mutations suggests that the collection saturates the genes readily mutable to a ts lethal phenotype in S. typhimurium. Physiological characteristics of the ts lethal mutants were tested: 6% of the mutants can grow at high temperature under anaerobic conditions, 17% can grow when the medium includes 0.5 M KCl, and 9% of the mutants die after a 2-hr incubation at the nonpermissive temperature. Most ts lethal mutations in this collection probably affect genes required for growth at all temperatures (not merely during high temperature growth) since Tn10 insertions that cause a temperature-sensitive lethal phenotype are rare.

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