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相关概念视频

Interference and Diffraction02:18

Interference and Diffraction

51.7K
Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a resulting wave with enhanced amplitude is produced. This is known as constructive interference. In this case, the two waves interacting are in phase with each other.
51.7K
Propagation of Waves01:07

Propagation of Waves

2.8K
When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second medium. In such a case, the interface of the two mediums can be considered as a boundary that is neither fixed nor free.
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
2.8K
X-ray Crystallography02:18

X-ray Crystallography

25.7K
The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
25.7K
Properties of DTFT II01:24

Properties of DTFT II

518
In the study of discrete-time signal processing, understanding the properties of the Discrete-Time Fourier Transform (DTFT) is crucial for analyzing and manipulating signals in the frequency domain. Several properties, including frequency differentiation, convolution, accumulation, and Parseval's relation, offer powerful tools for signal analysis.
The frequency differentiation property is illustrated by considering a DTFT pair and differentiating both sides with respect to ω.
518
Discrete Fourier Transform01:15

Discrete Fourier Transform

853
The Discrete Fourier Transform (DFT) is a fundamental tool in signal processing, extending the discrete-time Fourier transform by evaluating discrete signals at uniformly spaced frequency intervals. This transformation converts a finite sequence of time-domain samples into frequency components, each representing complex sinusoids ordered by frequency. The DFT translates these sequences into the frequency domain, effectively indicating the magnitude and phase of each frequency component present...
853
Properties of DTFT I01:24

Properties of DTFT I

737
In signal processing, Discrete-Time Fourier Transforms (DTFTs) play a critical role in analyzing discrete-time signals in the frequency domain. Various properties of the DTFTs such as linearity, time-shifting, frequency-shifting, time reversal, conjugation, and time scaling help understand and manipulate these signals for different applications.
The linearity property of DTFTs is fundamental. If two discrete-time signals are multiplied by constants a and b respectively, and then combined to...
737

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相关实验视频

Updated: Jan 17, 2026

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans
08:24

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans

Published on: September 13, 2017

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通过哈尔波束变换的数值衍射传播.

Yu Xiao, Changcheng Duan, Hao Peng

    Optics express
    |September 23, 2025
    PubMed
    概括

    这项研究引入了一种新的基于哈尔波束转换的方法 (HWTM) 用于光学模拟. HWTM克服了基于FT技术的采样局限性,提高了衍射建模的准确性和计算效率.

    科学领域:

    • 光学和光子学 在光学和光子学.
    • 计算物理 计算物理
    • 数字信号处理 数字信号处理

    背景情况:

    • 基于快速里叶变换 (FFT) 的数值衍射方法对于像数字全息学这样的光学模拟至关重要.
    • 这些方法由于声功能而受到采样限制,影响精度,传播距离和观测区域大小.
    • 现有的平面波基方法,如角光谱方法,面临着别名化问题.

    研究的目的:

    • 开发一种新的数值衍射方法,克服基于FT的采样技术的采样限制.
    • 在弗雷内尔衍射范围内的光学模拟中提高精度和计算效率.
    • 为更广泛的应用适应该方法,包括雷利-索默菲尔德衍射和离轴场景.

    主要方法:

    • 利用哈尔波段为输入波模型的基础,提供高效和自然离散的表示.
    • 实施基于哈尔波纹转换的方法 (HWTM) 以消除与声函数相关的样本别名问题.
    • 实现输出场的灵活采样,以提高准确性和效率.

    主要成果:

    • HWTM有效地消除了基于FT的声函数采样中固有的样本转移问题.
    • 该方法证明了弗雷内尔衍射的增强精度和计算效率.
    • 模拟实验证实了HWTM相对于传统的FFT方法的优势.

    更多相关视频

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    Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
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    Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

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    Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans

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    Quantifying Microorganisms at Low Concentrations Using Digital Holographic Microscopy DHM
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    Quantifying Microorganisms at Low Concentrations Using Digital Holographic Microscopy DHM

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    Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
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    Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

    Published on: August 22, 2017

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    结论:

    • 基于哈尔波形变换的方法 (HWTM) 为数字衍射提供了基于FFT的技术的优质替代方案.
    • 在光学模拟中,HWTM提供了更高的精度,计算效率和采样灵活性.
    • 该方法的适应性使其适用于各种衍射模式和配置.